powerpc/kexec_file: Add of_node_put() before goto

Fix following coccicheck warning:
./arch/powerpc/kexec/file_load_64.c:698:1-22: WARNING: Function
for_each_node_by_type should have of_node_put() before goto

Early exits from for_each_node_by_type should decrement the
node reference counter.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211018015418.10182-1-wanjiabing@vivo.com

arch/powerpc/kexec/file_load_64.c

@@ -700,6 +700,7 @@ static int update_usable_mem_fdt(void *fdt, struct crash_mem *usable_mem)
 		if (ret) {
 			pr_err("Failed to set linux,usable-memory property for %s node",
 			       dn->full_name);
+			of_node_put(dn);
 			goto out;
 		}
 	}