ARM: SAMSUNG: Fix Section mismatch in samsung_bl_set()

WARNING: vmlinux.o(.text+0xf47c): Section mismatch in reference from the function samsung_bl_set() to the (unknown reference) .init.data:(unknown)
The function samsung_bl_set() references
the (unknown reference) __initdata (unknown).
This is often because samsung_bl_set lacks a __initdata
annotation or the annotation of (unknown) is wrong.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>