powerpc/xics: fix refcount leak in icp_opal_init()

The of_find_compatible_node() function returns a node pointer with
refcount incremented, use of_node_put() on it when done.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220402013419.2410298-1-lv.ruyi@zte.com.cn

arch/powerpc/sysdev/xics/icp-opal.c

@@ -196,6 +196,7 @@ int __init icp_opal_init(void)
 
 	printk("XICS: Using OPAL ICP fallbacks\n");
 
+	of_node_put(np);
 	return 0;
 }