backlight: tdo24m: fix checkpatch warning

This patch fixes the checkpatch warning as below:

  WARNING: please, no space before tabs
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>