ALSA: hda/hdmi: fix without unlocked before return

Fix the following coccicheck warning:
sound/pci/hda/patch_hdmi.c:1852:2-8: preceding lock on line 1846

After add sanity check to pass klockwork check,
The spdif_mutex should be unlock before return true
in check_non_pcm_per_cvt().

Fixes: 960a581e

 ("ALSA: hda: fix some klockwork scan warnings")
Signed-off-by: Wu Bo <wubo40@huawei.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1587907042-694161-1-git-send-email-wubo40@huawei.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>