The backlight and LCD class _store functions currently accept values like "34
some random strings" without error.  This corrects them to return -EINVAL if
the value is not numeric with an optional byte of trailing whitespace.
Signed-off-by: NRichard Purdie <rpurdie@rpsys.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>