ALSA: snd-aoa: add of_node_put() in error path

ALSA: snd-aoa: add of_node_put() in error path

 Both calls to of_find_node_by_name() and of_get_next_child() return a
node pointer with refcount incremented thus it must be explicidly
decremented here after the last usage. As we are assured to have a
refcounted  np  either from the initial
of_find_node_by_name(NULL, name); or from the of_get_next_child(gpio, np)
in the while loop if we reached the error code path below, an
x of_node_put(np) is needed.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: commit f3d9478b2ce4 ("[ALSA] snd-aoa: add snd-aoa")
Signed-off-by: Takashi Iwai <tiwai@suse.de>