drm/amd/powerplay: Followup fixes to mc_reg_address

This is a followup to:
drm/amd/powerplay: Fix buffer overflows with mc_reg_address

Rework *_set_mc_special_registers for the other architectures to
use the same logic as the first patch. This allows the last entry
of the array to be filled without an error message for example.
This doesn't fix any known problems, perhaps avoided by luck.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ernst Sjöstrand <ernstp@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>