drm/amd/display: fix pstate allow handling in dcn2

[why]
pstate allow/block is not being handled properly on DCN2

[how]
DML needs to be updated to calculate pstate support at both min and max
mpc combine rather than just min
clock manager needs to update current to new pstate support before
sending to pplib/smu

Signed-off-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>