ASoC: SOF: imx8: fix memory allocation failure check on priv->pd_dev

ASoC: SOF: imx8: fix memory allocation failure check on priv->pd_dev

The memory allocation failure check for priv->pd_dev is incorrectly
pointer checking priv instead of priv->pd_dev. Fix this.

Addresses-Coverity: ("Logically dead code")
Fixes: 202acc565a1f ("ASoC: SOF: imx: Add i.MX8 HW support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191204124816.1415359-1-colin.king@canonical.com
Signed-off-by: Mark Brown <broonie@kernel.org>