ALSA: hda - correct bracketing in spdif test in patch_sigmatel.c

Noticed by sparse:
sound/pci/hda/patch_sigmatel.c:1285:43: warning: dubious: !x & y

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: Matthew Ranostay <mranostay@embeddedalley.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>