ARM: sa1100/assabet: include platform_device.h directly

ARM: sa1100/assabet: include platform_device.h directly

Patch "16559ae kgdb: remove #include <linux/serial_8250.h> from kgdb.h
caused assabet_defconfig to fail, since assabet.c did not
itself include linux/platform_device.h, although it needs it:

In file included from include/linux/mfd/ucb1x00.h:13:0,
                 from arch/arm/mach-sa1100/assabet.c:19:
include/linux/mfd/mcp.h:22:16: error: field 'attached_device' has incomplete type
include/linux/mfd/mcp.h:48:23: error: field 'drv' has incomplete type
In file included from arch/arm/mach-sa1100/assabet.c:19:0:
include/linux/mfd/ucb1x00.h:137:16: error: field 'dev' has incomplete type
arch/arm/mach-sa1100/assabet.c: In function 'assabet_init':
arch/arm/mach-sa1100/assabet.c:343:3: error: implicit declaration of function 'platform_device_register_simple' [-Wimplicit-function-declaration]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>