drm/amd/display: fix incorrect page table address for renoir

Incorrect page table address and programming sys aperture for
stutter gather, so fix it.

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>