drm/msm/a6xx: fix crashstate capture for A650

A650 has a separate RSCC region, so dump RSCC registers separately, reading
them from the RSCC base. Without this change a GPU hang will cause a system
reset if CONFIG_DEV_COREDUMP is enabled.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>