ALSA: xen: Use standard pcm_format_to_bits() for ALSA format bits

The open codes with the bit shift in xen_snd_front_alsa.c give sparse
warnings as the PCM format type is with __bitwise.
There is already a standard macro to get the format bits, so let's use
it instead.

This fixes sparse warnings like:
  sound/xen/xen_snd_front_alsa.c:191:47: warning: restricted snd_pcm_format_t degrades to integer
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/xen/xen_snd_front_alsa.c

@@ -188,7 +188,7 @@ static u64 to_sndif_formats_mask(u64 alsa_formats)
 
 	mask = 0;
 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
-		if (1 << ALSA_SNDIF_FORMATS[i].alsa & alsa_formats)
+		if (pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa) & alsa_formats)
 			mask |= 1 << ALSA_SNDIF_FORMATS[i].sndif;
 
 	return mask;
@@ -202,7 +202,7 @@ static u64 to_alsa_formats_mask(u64 sndif_formats)
 	mask = 0;
 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
 		if (1 << ALSA_SNDIF_FORMATS[i].sndif & sndif_formats)
-			mask |= 1 << ALSA_SNDIF_FORMATS[i].alsa;
+			mask |= pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa);
 
 	return mask;
 }