drm/amd/display: MPC updates

Fix update_mpcc logic to only call assert_mpcc_idle_before_connect
if mpcc is not already being used (and required removal).
Update set_out_rate_control to include optional flow control parameter.
In init_mpcc_from_hw check for case where bot_sel is same as mpcc_id.

Signed-off-by: Eric Bernstein <eric.bernstein@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>