[ln882h] Fix flashing with .bin/raw file (#81)

Author: Fumon

ltchiptool/soc/ln882h/util/ln882htool.py

@@ -208,7 +208,7 @@ def flash_write(
 
         # Convert stream to temporary file before sending with YMODEM
         with NamedTemporaryFile(delete=False) as f:
-            f.write(stream.getbuffer())
+            f.write(stream.read())
 
         self.command(f"upgrade", waitresp=False)