backlight: ams369fg06: use devm_{backlight,lcd}_device_register()

Use devm_backlight_device_register() and devm_lcd_device_register() to
make cleanup paths simpler.

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