ARM: pxa: fix USB gadget driver compilation regression

After commit 88f718e3
"ARM: pxa: delete the custom GPIO header" a compilation
error was introduced in the PXA25x gadget driver.
An attempt to fix the problem was made in
commit b144e4ab
"usb: gadget: fix pxa25x compilation problems"
by explictly stating the driver needs the <mach/hardware.h>
header, which solved the compilation for a few boards,
such as the pxa255-idp and its defconfig.

However the Lubbock board has this special clause in
drivers/usb/gadget/pxa25x_udc.c:

This include file has an implicit dependency on
<mach/irqs.h> having been included before <mach/lubbock.h>
was included.

Before commit 88f718e3
"ARM: pxa: delete the custom GPIO header" this implicit
dependency for the pxa25x_udc compile on the Lubbock was
satisfied by <linux/gpio.h> implicitly including
<mach/gpio.h> which was in turn including <mach/irqs.h>,
apart from the earlier added <mach/hardware.h>.

Fix this by having the PXA25x <mach/lubbock.h> explicitly
include <mach/irqs.h>.

Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Greg Kroah-Hartmann <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>