drm/msm/a6xx: Rebase GMU register offsets

drm/msm/a6xx: Rebase GMU register offsets

GMU registers are always at a fixed offset from the GPU base address,
a consistency maintained at least within a given architecture generation.
In A8x family, the base address of the GMU has changed, but the offsets
of the gmu registers remain largely the same. To enable reuse of the gmu
code for A8x chipsets, update the gmu register offsets to be relative
to the GPU's base address instead of GMU's.

Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/689010/
Message-ID: <20251118-kaana-gpu-support-v4-10-86eeb8e93fb6@oss.qualcomm.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>