drm/msm/a6xx: Improve MX rail fallback in RPMH vote init

drm/msm/a6xx: Improve MX rail fallback in RPMH vote init

Current logic assumes that the voltage corners in both MxG and MxA are
always same. This is not true for recent targets. So, rework the rpmh init
sequence to probe and calculate the votes with the respective rails, ie,
GX rails should use MxG as secondary rail and Cx rail should use MxA as
the secondary rail.

Fixes: d6225e0cd096 ("drm/msm/adreno: Add support for X185 GPU")
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/689014/
Message-ID: <20251118-kaana-gpu-support-v4-12-86eeb8e93fb6@oss.qualcomm.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>