drm/amd/display: Don't always set pstate true if dummy latency = 0

[Why]
If dummy pstate latency is 0 we should report the actual
pstate support, and not that pstate is always supported.

[How]
Don't always program pstate support true
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -2918,7 +2918,7 @@ bool dcn20_validate_bandwidth(struct dc *dc, struct dc_state *context,
 
 	if (context->bw_ctx.dml.soc.dummy_pstate_latency_us == 0 ||
 		(voltage_supported && full_pstate_supported)) {
-		context->bw_ctx.bw.dcn.clk.p_state_change_support = true;
+		context->bw_ctx.bw.dcn.clk.p_state_change_support = full_pstate_supported;
 		goto restore_dml_state;
 	}