drm/amd/pm: ensure the fw_info is not null before using it

This resolves the dereference null return value warning
reported by Coverity.
Signed-off-by: Tim Huang <tim.huang@amd.com>
Reviewed-by: Jesse Zhang <jesse.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1183,6 +1183,8 @@ static int init_overdrive_limits(struct pp_hwmgr *hwmgr,
 	fw_info = smu_atom_get_data_table(hwmgr->adev,
 			 GetIndexIntoMasterTable(DATA, FirmwareInfo),
 			 &size, &frev, &crev);
+	PP_ASSERT_WITH_CODE(fw_info != NULL,
+			    "Missing firmware info!", return -EINVAL);
 
 	if ((fw_info->ucTableFormatRevision == 1)
 	    && (le16_to_cpu(fw_info->usStructureSize) >= sizeof(ATOM_FIRMWARE_INFO_V1_4)))