backlight: l4f00242t03: export and use devm_gpio_request_one()

The devm_ functions allocate memory that is released when a driver
detaches.  This patch uses devm_gpio_request_one() for these functions.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Cc: Alberto Panizzo <alberto@amarulasolutions.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>