ALSA: x86: Drop suspicious U24 format support

U24 format is declared to be supported by the driver, but this looks
really doubtful, as there is no corresponding code.  Better to drop
it.  This format is very uncommon, so there should be practically no
impact by this change.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/x86/intel_hdmi_audio.c

@@ -136,8 +136,7 @@ static const struct snd_pcm_hardware had_pcm_hardware = {
 		SNDRV_PCM_INFO_MMAP|
 		SNDRV_PCM_INFO_MMAP_VALID |
 		SNDRV_PCM_INFO_BATCH),
-	.formats = (SNDRV_PCM_FMTBIT_S24 |
-		SNDRV_PCM_FMTBIT_U24),
+	.formats = SNDRV_PCM_FMTBIT_S24,
 	.rates = SNDRV_PCM_RATE_32000 |
 		SNDRV_PCM_RATE_44100 |
 		SNDRV_PCM_RATE_48000 |