Merge #1064

1064: Fix LoRaWAN PHY settings for SX126x driver r=Dirbaio a=jbeaurivage

While working on #1023 / #1041, I noticed that the `lorawan_device::PhyTxRx` implementation does not conform to the LoRaWAN standard, and therefore devices using this driver could never communicate with a gateway. This PR backports the changes I've made to fix the offending parameters, and I can confirm that the driver now works with LoRaWAN networks.

* Set preamble length to 8 symbols
* Set polarity to inverted for received messages

Co-authored-by: Justin Beaurivage <justin@wearableavionics.com>

embassy-lora/src/sx126x/mod.rs

@@ -87,7 +87,7 @@ where
                     config.rf.spreading_factor.into(),
                     config.rf.bandwidth.into(),
                     config.rf.coding_rate.into(),
-                    4,
+                    8,
                     false,
                     true,
                     false,
@@ -119,14 +119,14 @@ where
                     config.spreading_factor.into(),
                     config.bandwidth.into(),
                     config.coding_rate.into(),
-                    4,
+                    8,
                     4,
                     false,
                     0u8,
                     true,
                     false,
                     0,
-                    false,
+                    true,
                     true,
                 )
                 .await?;