Ensure that the radio is in an IDLE state before performing the LBT operation.

For regions where LBT is used the stack could end up in an end less loop displaying the following message:
```
...
###### ===== MCPS-Request ==== ######
STATUS      : Busy beacon reserved time

###### ===== MCPS-Request ==== ######
STATUS      : Busy beacon reserved time
...
```

The issue is that the LBT operation could happen when the beacon reception is started but before the `RxDone` or `RxTimeout` IRQ.

Author: mluis1

src/radio/sx126x/radio.c

@@ -562,6 +562,11 @@ bool RadioIsChannelFree( RadioModems_t modem, uint32_t freq, int16_t rssiThresh,
     int16_t rssi = 0;
     uint32_t carrierSenseTime = 0;
 
+    if( RadioGetStatus( ) != RF_IDLE )
+    {
+        return false;
+    }
+
     RadioSetModem( modem );
 
     RadioSetChannel( freq );

src/radio/sx1272/sx1272.c

@@ -260,6 +260,11 @@ bool SX1272IsChannelFree( RadioModems_t modem, uint32_t freq, int16_t rssiThresh
     int16_t rssi = 0;
     uint32_t carrierSenseTime = 0;
 
+    if( SX1272GetStatus( ) != RF_IDLE )
+    {
+        return false;
+    }
+
     SX1272SetModem( modem );
 
     SX1272SetChannel( freq );

src/radio/sx1276/sx1276.c

@@ -271,6 +271,11 @@ bool SX1276IsChannelFree( RadioModems_t modem, uint32_t freq, int16_t rssiThresh
     int16_t rssi = 0;
     uint32_t carrierSenseTime = 0;
 
+    if( SX1276GetStatus( ) != RF_IDLE )
+    {
+        return false;
+    }
+
     SX1276SetModem( modem );
 
     SX1276SetChannel( freq );