drm/msm: move msm_drm_register to async probe

To reduce boot time to first stage.

Before:
[    1.221918] init: init first stage started!

After:
[    1.208333] init: init first stage started!

Bug: 129688998
Test: reboot 100 times, camera, wifi, basic operation
Change-Id: If35e5b5aa5d83fb9412dcd6c7d5292cec3a7914e
Signed-off-by: Rick Yiu <rickyiu@google.com>