Revert "Disabled temporarily tx slot check for testing purposes (ARMmbed#2287)" (ARMmbed#2289)

This reverts commit 8cc0ff5.

Author: Jarkko Paso

source/Service_Libs/fhss/fhss_ws.c

@@ -587,10 +587,9 @@ static bool fhss_ws_check_tx_allowed(fhss_structure_t *fhss_structure)
      *         v
      * | BC | RX | TX | RX | TX | RX | TX | BC |
      */
-// Temporarily commented this check for testing purposes
-//    if (tx_slot_begin_ms < remaining_time_ms) {
-//        return false;
-//    }
+    if (tx_slot_begin_ms < remaining_time_ms) {
+        return false;
+    }
     tx_slot_begin_ms = tx_slot_begin_ms - (((tx_slot_begin_ms - remaining_time_ms) / (2 * fhss_structure->ws->txrx_slot_length_ms)) * (2 * fhss_structure->ws->txrx_slot_length_ms));
     uint32_t rx_slot_begin_ms = tx_slot_begin_ms - fhss_structure->ws->txrx_slot_length_ms;
     /* Check if we are currently on TX slot.