[Why & How]

It's useful to disable MPO when debugging or testing. Therefore, add a
dcdebugmask option to disable MPO.
Signed-off-by: NLeo Li <sunpeng.li@amd.com>
Reviewed-by: NRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>