Doxegen this chan_dahdi lock.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@251946 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -692,7 +692,7 @@ enum DAHDI_IFLIST {
 };
 struct dahdi_pvt {
-	ast_mutex_t lock;
+	ast_mutex_t lock;					/*!< Channel private lock. */
 	struct callerid_state *cs;
 	struct ast_channel *owner;			/*!< Our current active owner (if applicable) */
 							/*!< Up to three channels can be associated with this call */