drm/amd/pm: fix warning using uninitialized value of max_vid_step

Check the return of pp_atomfwctrl_get_Voltage_table_v4
as it may fail to initialize max_vid_step
V2: change the check condition (Tim Huang)
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_hwmgr.c

@@ -2573,8 +2573,11 @@ static int vega10_init_smc_table(struct pp_hwmgr *hwmgr)
 		}
 	}
 
-	pp_atomfwctrl_get_voltage_table_v4(hwmgr, VOLTAGE_TYPE_VDDC,
+	result = pp_atomfwctrl_get_voltage_table_v4(hwmgr, VOLTAGE_TYPE_VDDC,
 			VOLTAGE_OBJ_SVID2,  &voltage_table);
+	PP_ASSERT_WITH_CODE(!result,
+			"Failed to get voltage table!",
+			return result);
 	pp_table->MaxVidStep = voltage_table.max_vid_step;
 
 	pp_table->GfxDpmVoltageMode =