ARM: SAMSUNG: Add __init attribute to samsung_bl_set()

s3c_set_platdata() is defined with __init attribute, hence all functions
referencing this function should also be defined with __init attribute.

samsung_bl_set() is referenced only in '__init xxx_machine_init()' functions,
thus this change won't put any additional constraint on the usage of
samsung_bl_set().

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>