gsm0411_smr: Fix the size of the array

The code is lacking a "," at the end of a string and we ended up
doing string concatination instead of having an invalid state.

Fixes Coverity CID 1206564
diff --git a/src/gsm/gsm0411_smr.c b/src/gsm/gsm0411_smr.c
index a7e9d24..eb1f036 100644
--- a/src/gsm/gsm0411_smr.c
+++ b/src/gsm/gsm0411_smr.c
@@ -97,7 +97,7 @@
 static const char *smr_state_names[] = {
 	"IDLE",
 	"WAIT_FOR_RP_ACK",
-	"illegal state 2"
+	"illegal state 2",
 	"WAIT_TO_TX_RP_ACK",
 	"WAIT_FOR_RETRANS_T",
 };