drm/amd/display: use uclk pstate latency for fw assisted mclk validation dcn32

[WHY?]
DCN32 uses fclk pstate watermarks for dummy pstate, and must always be
supported.

[HOW?]
Validation needs to be run with fclk pstate latency set
as the dummy pstate latency to get correct prefetch and bandwidth outputs.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>