otherwise there will be DMAR reading error comes out from CP since
GFX is still alive and CPC's WPTR_POLL is still enabled, which would
lead to DMAR read error.

fix:
we can hault CPG after hw_fini, but cannot halt CPC becaues KIQ
stil need to be alive to let RLCV invoke, but its WPTR_POLL could
be disabled.
Signed-off-by: NMonk Liu <Monk.Liu@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>