[Why]
It's an interface violation to use infinite loops within DMUB
service functions and we'll lock up the kernel by doing so.

[How]
Revert the function back to its intended functionality.
Move the infinite loops into DC/DM as necessary.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>