kgsl/drm: add self refresh workqueue to support updating.

This patch adds self refresh routine for self updating to user space.

Change-Id: If5afdc1052b3f55f896227aca182aba51c6e4c0b
Signed-off-by: Eunchul Kim <chulspro.kim@samsung.com>
Signed-off-by: Mathew Karimpanal <kjmathew@codeaurora.org>
(cherry picked from commit 98b8d3a08322d9964ade3490128d7e317ce83d06)