ARM: imx: compile fix for hotplug.c

Commit bca7a5a0

 (ARM: cpu hotplug: remove majority of cache flushing
from platforms) removes include of <asm/cacheflush.h> and hence
discovers a few indirect inclusion and declaration problems as below.

  CC      arch/arm/mach-imx/hotplug.o
In file included from arch/arm/mach-imx/hotplug.c:16:0:
arch/arm/mach-imx/common.h:100:29: warning: ‘struct pt_regs’ declared inside parameter list [enabled by default]
arch/arm/mach-imx/common.h:100:29: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]
arch/arm/mach-imx/common.h:101:29: warning: ‘struct pt_regs’ declared inside parameter list [enabled by default]
arch/arm/mach-imx/hotplug.c: In function ‘imx_cpu_die’:
arch/arm/mach-imx/hotplug.c:53:2: error: implicit declaration of function ‘cpu_do_idle’ [-Werror=implicit-function-declaration]
arch/arm/mach-imx/hotplug.c: In function ‘imx_cpu_kill’:
arch/arm/mach-imx/hotplug.c:58:26: error: ‘jiffies’ undeclared (first use in this function)
arch/arm/mach-imx/hotplug.c:58:26: note: each undeclared identifier is reported only once for each function it appears in
arch/arm/mach-imx/hotplug.c:58:2: error: implicit declaration of function ‘msecs_to_jiffies’ [-Werror=implicit-function-declaration]
arch/arm/mach-imx/hotplug.c:61:3: error: implicit declaration of function ‘time_after’ [-Werror=implicit-function-declaration]

Fix them by adding the needed inclusion and declaration.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Olof Johansson <olof@lixom.net>