ASoC: eukrea-tlv320: Fix of_node_put() call with uninitialized object

ASoC: eukrea-tlv320: Fix of_node_put() call with uninitialized object

The of_node_put() call in eukrea_tlv320_probe() may take an
uninitialized pointer, as compiler spotted out:
  sound/soc/fsl/eukrea-tlv320.c:221:14: warning: 'ssi_np' may be used uninitialized in this function [-Wuninitialized]

This patch adds the proper NULL initializations as a fix.
(codec_np is also NULL initialized just for consistency.)

Fixes: 66f232908de2 ('ASoC: eukrea-tlv320: Add DT support')
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>