Add support for drmModeAtomicCommit

Add support for drmModeAtomicCommit

Current display commit API drmModeSetPlane() takes too much time
and its caller tdm_layer_commit() holds a lock "private_display->lock"
which is also needed by other thread, it makes performance low.

In order to solve this problem, we need an asynchronous API to do
this job which is drmModeAtomicCommit() here.

Patch's modification includes:
1. Change display commit method to drmModeAtomicCommit.
2. Disable vblank wait event in function vc4_output_commit()
since it's not necessary any more for atomic mode.
3. Create an event and pass it to _tdm_vc4_display_commit_layer()
which is used to API finish callback.

Change-Id: If2ba5c80bcd553cdd7f4cd04364d1e40d203dc10