Make RegFifoTxBaseAddr and RegFifoRxBaseAddr registers use configurable

In LoRa::new these are set to 0 which is not default (RegFifoTxBaseAddr
is 0x80 after reset). This however cannot be modified after LoRa
structure creation - so e.g. in LoRa::configure it cannot be configured
back to the same value (0) as in LoRa::new.

src/lib.rs

@@ -222,8 +222,8 @@ where
         if version == VERSION_CHECK {
             sx127x.set_mode(RadioMode::Sleep)?;
             sx127x.set_frequency(frequency)?;
-            sx127x.write_register(Register::RegFifoTxBaseAddr.addr(), 0)?;
-            sx127x.write_register(Register::RegFifoRxBaseAddr.addr(), 0)?;
+            sx127x.set_fifo_tx_base(0)?;
+            sx127x.set_fifo_rx_base(0)?;
             let lna = sx127x.read_register(Register::RegLna.addr())?;
             sx127x.write_register(Register::RegLna.addr(), lna | 0x03)?;
             sx127x.write_register(Register::RegModemConfig3.addr(), 0x04)?;
@@ -734,6 +734,22 @@ where
 
         self.write_register(Register::RegPaRamp as u8, pa_ramp)
     }
+
+    pub fn set_fifo_rx_base(
+        &mut self,
+        base_addr: u8,
+    ) -> Result<(), Error<E, CS::Error, RESET::Error>> {
+        self.write_register(Register::RegFifoRxBaseAddr.addr(), base_addr)?;
+        Ok(())
+    }
+
+    pub fn set_fifo_tx_base(
+        &mut self,
+        base_addr: u8,
+    ) -> Result<(), Error<E, CS::Error, RESET::Error>> {
+        self.write_register(Register::RegFifoTxBaseAddr.addr(), base_addr)?;
+        Ok(())
+    }
 }
 /// Modes of the radio and their corresponding register values.
 #[derive(Clone, Copy)]