As pointed out by Akhil during the review process of GMU wrapper
introduction [1], it makes sense to move this write into the function
that's responsible for forcibly shutting the GMU off.

It is also very convenient to move this to GMU-specific code, so that
it does not have to be guarded by an if-condition to avoid calling it
on GMU wrapper targets.

Move the write to the aforementioned a6xx_gmu_force_off() to achieve
that. No effective functional change.

[1] https://lore.kernel.org/linux-arm-msm/20230501194022.GA18382@akhilpo-linux.qualcomm.com/Reviewed-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/542752/Signed-off-by: Rob Clark <robdclark@chromium.org>