Export pcm_mmap_avail

This is useful for timer based wakeups and for checking how much data
has been captured by a hotwording device.

Change-Id: I409201a5c9ce73abc807a9dd767beb3a32810f06
Signed-off-by: Dylan Reid <dgreid@chromium.org>

include/tinyalsa/asoundlib.h

@@ -235,6 +235,7 @@ int pcm_mmap_read(struct pcm *pcm, void *data, unsigned int count);
 int pcm_mmap_begin(struct pcm *pcm, void **areas, unsigned int *offset,
                    unsigned int *frames);
 int pcm_mmap_commit(struct pcm *pcm, unsigned int offset, unsigned int frames);
+int pcm_mmap_avail(struct pcm *pcm);
 
 /* Prepare the PCM substream to be triggerable */
 int pcm_prepare(struct pcm *pcm);

pcm.c

@@ -1059,7 +1059,7 @@ static inline int pcm_mmap_capture_avail(struct pcm *pcm)
     return avail;
 }
 
-static inline int pcm_mmap_avail(struct pcm *pcm)
+int pcm_mmap_avail(struct pcm *pcm)
 {
     pcm_sync_ptr(pcm, SNDRV_PCM_SYNC_PTR_HWSYNC);
     if (pcm->flags & PCM_IN)