ARM: integrator: include <linux/export.h>

Without this patch, building integrator_defconfig results in:

arch/arm/mach-integrator/core.c:150:1: warning: data definition has no type or storage class [enabled by default]
arch/arm/mach-integrator/core.c:150:1: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL' [-Wimplicit-int]
arch/arm/mach-integrator/core.c:150:1: warning: parameter names (without types) in function declaration [enabled by default]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>