drm/msm/a8xx: Preemption support for A840

drm/msm/a8xx: Preemption support for A840

The programing sequence related to preemption is unchanged from A7x. But
there is some code churn due to register shuffling in A8x. So, split out
the common code into a header file for code sharing and add/update
additional changes required to support preemption feature on A8x GPUs.

Finally, enable the preemption quirk in A840's catalog to enable this
feature.

Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/714682/
Message-ID: <20260327-a8xx-gpu-batch2-v2-15-2b53c38d2101@oss.qualcomm.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>