drm/amd/display: Fix register definitions for DCN32/321

[Why & How]
Fix the instatiation sequence for MPC registers and add a few other
missing register definitions that were ommited erroneously when copying
them over to enable runtime initialization of reigster offsets for
DCN32/321

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>