backlight: hp680_bl: fix checkpatch error and warning

This patch fixes the checkpatch error and warning as below:

  WARNING: please, no space before tabs
  WARNING: please, no spaces at the start of a line
  ERROR: do not initialise statics to 0 or NULL
  ERROR: code indent should use tabs where possible

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