ASoC: tegra: Fix a NULL vs IS_ERR() check

The tegra_machine_parse_phandle() function doesn't return NULL, it returns
error pointers.

Fixes: cc8f70f5 ("ASoC: tegra: Unify ASoC machine drivers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/YMyjOKFsPe9SietU@mwanda


Signed-off-by: Mark Brown <broonie@kernel.org>