drm/msm/a5xx: fix context faults during ring switch

drm/msm/a5xx: fix context faults during ring switch

The rptr_addr is set in the preempt_init_ring(), which is called from
a5xx_gpu_init(). It uses shadowptr() to set the address, however the
shadow_iova is not yet initialized at that time. Move the rptr_addr
setting to the a5xx_preempt_hw_init() which is called after setting the
shadow_iova, getting the correct value for the address.

Fixes: 8907afb476ac ("drm/msm: Allow a5xx to mark the RPTR shadow as privileged")
Suggested-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/522640/
Link: https://lore.kernel.org/r/20230214020956.164473-5-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>