powerpc/kexec: fix for_each_child.cocci warning

for_each_node_by_type should have of_node_put() before return.

Generated by: scripts/coccinelle/iterators/for_each_child.cocci

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/alpine.DEB.2.22.394.2108031654080.17639@hadrien