i3c: master: Add of_node_put() before return

Each iteration of for_each_available_childe_of_node puts the previous
node, but in the case of a return from the middle of the loop, there
is no put, thus causing a memory leak. Add an of_node_put before the
return.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>