leds: max77650: Add of_node_put() before return

Each iteration of for_each_child_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.
Hence create a new label, err_node_put, which puts the previous node and
returns variable rv. Modify the mid-loop return statements to instead
store the return value in rv and jump to err_node_put.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>