[ALSA] Kill useless volatile in pcm.h

The volatile prefix is just useless there.  Let's kill them, and then
gcc will be happier, too.
   sound/acore/pcm.c:867: warning: passing argument 1 of ‘__constant_c_and_count_memset’ discards qualifiers from pointer target type
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@suse.cz>

include/sound/pcm.h

@@ -301,8 +301,8 @@ struct snd_pcm_runtime {
 	union snd_pcm_sync_id sync;	/* hardware synchronization ID */
 
 	/* -- mmap -- */
-	volatile struct snd_pcm_mmap_status *status;
-	volatile struct snd_pcm_mmap_control *control;
+	struct snd_pcm_mmap_status *status;
+	struct snd_pcm_mmap_control *control;
 
 	/* -- locking / scheduling -- */
 	wait_queue_head_t sleep;