[ALSA] PCM interface - rename SNDRV_PCM_TSTAMP_MMAP to SNDRV_PCM_TSTAMP_ENABLE

Change semantics for SNDRV_PCM_TSTAMP_MMAP. Doing timestamping only in
the interrupt handler might cause that hw_ptr is not related to actual
timestamp. With this change, grab timestamp at every hw_ptr update to
have always valid timestamp + ring buffer position pair.
With this change, SNDRV_PCM_TSTAMP_MMAP was renamed to
SNDRV_PCM_TSTAMP_ENABLE. It's no regression (I think).

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index ed0223c..1533f03 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -144,6 +144,8 @@
 {
 	snd_pcm_uframes_t pos;
 
+	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
+		snd_pcm_gettime(runtime, (struct timespec *)&runtime->status->tstamp);
 	pos = substream->ops->pointer(substream);
 	if (pos == SNDRV_PCM_POS_XRUN)
 		return pos; /* XRUN */
@@ -186,8 +188,6 @@
 	snd_pcm_uframes_t new_hw_ptr, hw_ptr_interrupt;
 	snd_pcm_sframes_t delta;
 
-	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_MMAP)
-		snd_pcm_gettime(runtime, (struct timespec *)&runtime->status->tstamp);
 	pos = snd_pcm_update_hw_ptr_pos(substream, runtime);
 	if (pos == SNDRV_PCM_POS_XRUN) {
 		xrun(substream);