[ALSA] PCM core - introduce CONFIG_SND_PCM_XRUN_DEBUG

This patch makes the XRUN (overrun/underrun) notification code optional.

Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/core/Kconfig b/sound/core/Kconfig
index 8efc1b1..f3a07fb 100644
--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -171,3 +171,13 @@
 	help
 	  Say Y here to enable extra-verbose log messages printed when
 	  detecting devices.
+
+config SND_PCM_XRUN_DEBUG
+	bool "Enable PCM ring buffer overrun/underrun debugging"
+	default n
+	depends on SND_DEBUG
+	help
+	  Say Y to enable the PCM ring buffer overrun/underrun debugging.
+	  It is usually not required, but if you have trouble with
+	  sound clicking when system is loaded, it may help to determine
+	  the process or driver which causes the scheduling gaps.