ASoC: tegra: Fix unused variable warning

Fixes: 2a8bd83a

 ("ASoC: tegra: Remove superfluous snd_soc_jack_free_gpios() call")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>