Rewrite the cxl_guest_init_afu() loop in cxl_of_probe() to use
for_each_child_of_node() rather than a hand-coded for loop.

Remove the useless of_node_put(afu_np) call after the loop, where it's
guaranteed that afu_np == NULL.
Reported-by: NSF Markus Elfring <elfring@users.sourceforge.net>
Reported-by: NJulia Lawall <julia.lawall@lip6.fr>
Signed-off-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Reviewed-by: NFrederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>