net: ath5k: fix build errors when linux/phy*.h is removed from net/dsa.h

Fix these errors reported by the 0-day builder by replacing the
linux/export.h include with linux/module.h.

In file included from include/linux/platform_device.h:14:0,
                 from drivers/net/wireless/ath/ath5k/ahb.c:20:
include/linux/device.h:1463:1: warning: data definition has no type or storage class
 module_init(__driver##_init); \
 ^
include/linux/platform_device.h:228:2: note: in expansion of macro 'module_driver'
  module_driver(__platform_driver, platform_driver_register, \
  ^~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~
include/linux/device.h:1463:1: error: type defaults to 'int' in declaration of 'module_init' [-Werror=implicit-int]
 module_init(__driver##_init); \
 ^
include/linux/platform_device.h:228:2: note: in expansion of macro 'module_driver'
  module_driver(__platform_driver, platform_driver_register, \
  ^~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: warning: parameter names (without types) in function declaration
In file included from include/linux/platform_device.h:14:0,
                 from drivers/net/wireless/ath/ath5k/ahb.c:20:
include/linux/device.h:1468:1: warning: data definition has no type or storage class
 module_exit(__driver##_exit);
 ^
include/linux/platform_device.h:228:2: note: in expansion of macro 'module_driver'
  module_driver(__platform_driver, platform_driver_register, \
  ^~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~
include/linux/device.h:1468:1: error: type defaults to 'int' in declaration of 'module_exit' [-Werror=implicit-int]
 module_exit(__driver##_exit);
 ^
include/linux/platform_device.h:228:2: note: in expansion of macro 'module_driver'
  module_driver(__platform_driver, platform_driver_register, \
  ^~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: warning: parameter names (without types) in function declaration
In file included from include/linux/platform_device.h:14:0,
                 from drivers/net/wireless/ath/ath5k/ahb.c:20:
drivers/net/wireless/ath/ath5k/ahb.c:233:24: warning: 'ath_ahb_driver_exit' defined but not used [-Wunused-function]
 module_platform_driver(ath_ahb_driver);
                        ^
include/linux/device.h:1464:20: note: in definition of macro 'module_driver'
 static void __exit __driver##_exit(void) \
                    ^~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:24: warning: 'ath_ahb_driver_init' defined but not used [-Wunused-function]
 module_platform_driver(ath_ahb_driver);
                        ^
include/linux/device.h:1459:19: note: in definition of macro 'module_driver'
 static int __init __driver##_init(void) \
                   ^~~~~~~~
drivers/net/wireless/ath/ath5k/ahb.c:233:1: note: in expansion of macro 'module_platform_driver'
 module_platform_driver(ath_ahb_driver);
 ^~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>