Fix some typos

Fix typos and common misspellings in code comments and log messages.

Change-Id: Ie66b89065f2100c1d2125ce5a6c9b1d58df7c8ad
diff --git a/src/libmsc/mncc_sock.c b/src/libmsc/mncc_sock.c
index 0a4e99b..670d692 100644
--- a/src/libmsc/mncc_sock.c
+++ b/src/libmsc/mncc_sock.c
@@ -82,7 +82,7 @@
 	/* re-enable the generation of ACCEPT for new connections */
 	state->listen_bfd.when |= BSC_FD_READ;
 
-	/* release all exisitng calls */
+	/* release all existing calls */
 	gsm0408_clear_all_trans(state->net, TRANS_CC);
 
 	/* flush the queue */