powerpc/powernv: Bail upon invalid master PE

When freezing compound PEs in pnv_ioda_freeze_pe(), we should bail
upon illegal master PE. We needn't freeze slave PE because it should
have been put into frozen state by hardware.
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/pci-ioda.c

@@ -373,7 +373,9 @@ static void pnv_ioda_freeze_pe(struct pnv_phb *phb, int pe_no)
 	/* Fetch master PE */
 	if (pe->flags & PNV_IODA_PE_SLAVE) {
 		pe = pe->master;
-		WARN_ON(!pe || !(pe->flags & PNV_IODA_PE_MASTER));
+		if (WARN_ON(!pe || !(pe->flags & PNV_IODA_PE_MASTER)))
+			return;
+
 		pe_no = pe->pe_number;
 	}