backlight: da903x_bl: use BL_CORE_SUSPENDRESUME option

Use BL_CORE_SUSPENDRESUME option to support suspend/resume.  It reduces
code size.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>