mmcli/cell-broadcast: Add status output

This allows to get the current channel list:

$ mmcli -m any  --cell-broadcast-status
  --------------------------
  Cell Broadcast | channels: 0-9999,4353

cli/mmcli-output.h

@@ -46,6 +46,7 @@ typedef enum {
     MMC_S_MODEM_3GPP_USSD,
     MMC_S_MODEM_3GPP_PROFILE_MANAGER,
     MMC_S_MODEM_CDMA,
+    MMC_S_MODEM_CELL_BROADCAST,
     MMC_S_MODEM_SIM,
     MMC_S_MODEM_BEARER,
     MMC_S_MODEM_TIME,
@@ -173,6 +174,8 @@ typedef enum {
     MMC_F_CDMA_REGISTRATION_CDMA1X,
     MMC_F_CDMA_REGISTRATION_EVDO,
     MMC_F_CDMA_ACTIVATION,
+    /* CellBroadcast section */
+    MMC_F_CELL_BROADCAST_CHANNELS,
     /* SIM section */
     MMC_F_SIM_PATH,
     MMC_F_SIM_PRIMARY_SLOT,