video/s3c: move platform_data out of arch/arm

The s3c-fb driver requires header files from the samsung platforms
to find its platform_data definition, but this no longer works on
multiplatform kernels, so let's move the data into a new header
file under include/linux/platform_data.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: linux-fbdev@vger.kernel.org
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>