video: s3c-fb: add runtime_get/put to suspend/resume

This patch adds runtime_get/put to suspend/resume, which should be
necessary to prevent the problem to access the fimd register
without block power on.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>