subghz: Allow custom lora sync word (#383)

* subghz: allow custom lora sync word

* LoRaSyncWord: fix linting

Author: huming2207

hal/src/subghz/lora_sync_word.rs

@@ -8,13 +8,16 @@ pub enum LoRaSyncWord {
     Private,
     /// LoRa public network.
     Public,
+    /// Custom sync word
+    Custom([u8; 2]),
 }
 
 impl LoRaSyncWord {
     pub(crate) const fn bytes(self) -> [u8; 2] {
         match self {
             LoRaSyncWord::Private => [0x14, 0x24],
             LoRaSyncWord::Public => [0x34, 0x44],
+            LoRaSyncWord::Custom(buf) => buf,
         }
     }
 }