drm/msm/a6xx: Add missing aperture_lock init

drm/msm/a6xx: Add missing aperture_lock init

Looks like this was somehow missed when introducing gen8 support.

Fixes: 288a93200892 ("drm/msm/adreno: Introduce A8x GPU Support")
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/713545/
Message-ID: <20260323161603.1165108-1-robin.clark@oss.qualcomm.com>