ASoC: atmel: Add missing of_node_put() in at91sam9g20ek_audio_probe

ASoC: atmel: Add missing of_node_put() in at91sam9g20ek_audio_probe

This node pointer is returned by of_parse_phandle() with refcount
incremented in this function.
Calling of_node_put() to avoid the refcount leak.

Fixes: c789859b4066 ("ASoC: at91sam9g20ek-wm8731: convert to dt support")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20220307124539.1743-1-linmq006@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>