drm/msm/a6xx: Add support for Adreno 612

drm/msm/a6xx: Add support for Adreno 612

Add support for Adreno 612 GPU found in SM6150/QCS615 chipsets.
A612 falls under ADRENO_6XX_GEN1 family and is a cut down version
of A615 GPU.

A612 has a new IP called Reduced Graphics Management Unit or RGMU
which is a small state machine which helps to toggle GX GDSC
(connected to CX rail) to implement IFPC feature. It doesn't support
any other features of a full fledged GMU like clock control, resource
voting to rpmh etc. So we need linux clock driver support like other
gmu-wrapper implementations to control gpu core clock and gpu GX gdsc.
This patch skips RGMU core initialization and act more like a
gmu-wrapper case.

Signed-off-by: Jie Zhang <quic_jiezh@quicinc.com>
Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/686212/
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>