bluetooth: add slip SLIP_ESC case break

H5 SLIP_ESC magic payload whould be encode with
SLIP_ESC and SLIP_ESC_ESC

Signed-off-by: chengkai <chengkai@xiaomi.com>

drivers/wireless/bluetooth/bt_slip.c

@@ -320,6 +320,7 @@ static uint8_t *bt_slip_slip_byte(FAR uint8_t *packet, FAR uint8_t byte)
       packet[0] = SLIP_ESC;
       packet[1] = SLIP_ESC_ESC;
       offset = 2;
+      break;
     default:
       packet[0] = byte;
       break;