backlight: lp855x: remove unnecessary parentheses

Remove unnecessary parentheses in order to fix the following checkpatch
error.

  ERROR: return is not a function, parentheses are not required

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