drm/amd/pm: suppress static checker warning

Suppress the warning below:
drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/hardwaremanager.c:274 phm_check_smc_update_required_for_display_configuration()
warn: signedness bug returning '(-22)'
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -271,7 +271,10 @@ int phm_start_thermal_controller(struct pp_hwmgr *hwmgr)
 
 bool phm_check_smc_update_required_for_display_configuration(struct pp_hwmgr *hwmgr)
 {
-	PHM_FUNC_CHECK(hwmgr);
+	if (hwmgr == NULL ||
+	    hwmgr->hwmgr_func == NULL)
+		return false;
+
 	if (hwmgr->pp_one_vf)
 		return false;