ARM: S3C24XX: add missing platform_device.h include for osiris

The missing include led to a implcit declaration warning:

In file included from arch/arm/mach-s3c24xx/mach-osiris.c:34:0:
include/linux/platform_data/i2c-s3c2410.h:37:26: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:37:26: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:66:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:67:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:68:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:69:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:70:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:71:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:72:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]
include/linux/platform_data/i2c-s3c2410.h:73:38: warning: 'struct platform_device' declared inside parameter list [enabled by default]

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>