broadband-modem: add another Novatel +GCAP LTE response

This time from the 551L.  I wonder when they'll make up their minds
about what to return.

src/mm-broadband-modem.c

@@ -340,6 +340,7 @@ typedef struct {
 static const ModemCaps modem_caps[] = {
     { "+CGSM",     MM_MODEM_CAPABILITY_GSM_UMTS  },
     { "+CLTE2",    MM_MODEM_CAPABILITY_LTE       }, /* Novatel */
+    { "+CLTE1",    MM_MODEM_CAPABILITY_LTE       }, /* Novatel */
     { "+CLTE",     MM_MODEM_CAPABILITY_LTE       },
     { "+CIS707-A", MM_MODEM_CAPABILITY_CDMA_EVDO },
     { "+CIS707A",  MM_MODEM_CAPABILITY_CDMA_EVDO }, /* Cmotech */