drm/msm/adreno: Implement gx_is_on() for A8x

drm/msm/adreno: Implement gx_is_on() for A8x

A8x has a diverged enough for a separate implementation of gx_is_on()
check. Add that and move them to the adreno func table.

Fixes: 288a93200892 ("drm/msm/adreno: Introduce A8x GPU Support")
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/714661/
Message-ID: <20260327-a8xx-gpu-batch2-v2-5-2b53c38d2101@oss.qualcomm.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>