Fix sync word parameter type

The valid range is between 0x11-0xff

Author: szotsaki

src/LoRa.cpp

@@ -411,7 +411,7 @@ void LoRaClass::setPreambleLength(long length)
   writeRegister(REG_PREAMBLE_LSB, (uint8_t)(length >> 0));
 }
 
-void LoRaClass::setSyncWord(int sw)
+void LoRaClass::setSyncWord(uint8_t sw)
 {
   writeRegister(REG_SYNC_WORD, sw);
 }

src/LoRa.h

@@ -81,7 +81,7 @@ class LoRaClass : public Stream {
   void setSignalBandwidth(long sbw);
   void setCodingRate4(int denominator);
   void setPreambleLength(long length);
-  void setSyncWord(int sw);
+  void setSyncWord(uint8_t sw);
   void enableLowDataRateOptimize(bool enabled);
   void enableCrc();
   void disableCrc();