gsm/lapd_core: Make sure rc is initialize in lapd_rx_u

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/gsm/lapd_core.c b/src/gsm/lapd_core.c
index 54adbca..c81c2fb 100644
--- a/src/gsm/lapd_core.c
+++ b/src/gsm/lapd_core.c
@@ -782,7 +782,7 @@
 {
 	struct lapd_datalink *dl = lctx->dl;
 	int length = lctx->length;
-	int rc;
+	int rc = 0;
 	uint8_t prim, op;
 
 	switch (lctx->s_u) {