powerpc/kexec: Fix build failure from uninitialised variable

clang 14 won't build because ret is uninitialised and can be returned if
both prop and fdtprop are NULL.  Drop the ret variable and return an
error in that failure case.

Fixes: b1fc44ea ("pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window")
Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220810054331.373761-1-ruscur@russell.cc

arch/powerpc/kexec/file_load_64.c

@@ -1043,17 +1043,17 @@ static int copy_property(void *fdt, int node_offset, const struct device_node *d
 			 const char *propname)
 {
 	const void *prop, *fdtprop;
-	int len = 0, fdtlen = 0, ret;
+	int len = 0, fdtlen = 0;
 
 	prop = of_get_property(dn, propname, &len);
 	fdtprop = fdt_getprop(fdt, node_offset, propname, &fdtlen);
 
 	if (fdtprop && !prop)
-		ret = fdt_delprop(fdt, node_offset, propname);
+		return fdt_delprop(fdt, node_offset, propname);
 	else if (prop)
-		ret = fdt_setprop(fdt, node_offset, propname, prop, len);
-
-	return ret;
+		return fdt_setprop(fdt, node_offset, propname, prop, len);
+	else
+		return -FDT_ERR_NOTFOUND;
 }
 
 static int update_pci_dma_nodes(void *fdt, const char *dmapropname)