ALSA: pcm: Add xrun counter for snd_pcm_substream

ALSA: pcm: Add xrun counter for snd_pcm_substream

This patch adds an xrun counter to snd_pcm_substream as an alternative
to using logs from XRUN_DEBUG_BASIC. The counter provides a way to track
the number of xrun occurences, accessible through the /proc interface.

The counter is enabled when CONFIG_SND_PCM_XRUN_DEBUG is set.

Example output:

$ cat /proc/asound/card0/pcm9p/sub0/status

owner_pid   : 1425
trigger_time: 235.248957291
tstamp      : 0.000000000
delay       : 1912
avail       : 480
avail_max   : 1920
-----
hw_ptr      : 672000
appl_ptr    : 673440
xrun_counter: 3  # (new row)

Signed-off-by: Norman Bintang <normanbt@chromium.org>
Reviewed-by: Chih-Yang Hsia <paulhsia@chromium.org>
Tested-by: Chih-Yang Hsia <paulhsia@chromium.org>
Reviewed-by: David Riley <davidriley@chromium.org>
Link: https://patch.msgid.link/20240809140648.3414349-1-normanbt@chromium.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>