backlight: lm3630: fix sparse warning

This patch is to fix sparse warning due to mixing different enum type.

Signed-off-by: Daniel Jeong <gshark.jeong@gmail.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>