drm/amd/display: Handle Unknown Result for SMU Periodic Retraining on DCN2.1

[WHY & HOW]
Currently if VBIOSSMC_Result_UnknownCmd is returned as result of smu msg
there is no way to know.  Put 1 in param so if 1 is returned, this unknown case is handled.
Signed-off-by: Sung Lee <sung.lee@amd.com>
Acked-by: Bindu Ramamurthy <bindu.r@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr_vbios_smu.c

@@ -247,5 +247,6 @@ int rn_vbios_smu_is_periodic_retraining_disabled(struct clk_mgr_internal *clk_mg
 	return rn_vbios_smu_send_msg_with_param(
 			clk_mgr,
 			VBIOSSMC_MSG_IsPeriodicRetrainingDisabled,
-			0);
+			1);	// if PMFW doesn't support this message, assume retraining is disabled
+				// so we only use most optimal watermark if we know retraining is enabled.
 }