drm/komeda: Add komeda_crtc_atomic_flush

A komeda flush is comprised two steps:
1. update pipeline/component state to HW.
2. call dev_func->flush to notify HW to kickoff the update.

Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>