drivers/video/backlight/l4f00242t03.c: use gpio_request_one() to simplify error handling

Using gpio_request_one can make the error handling simpler.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.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>