[ln882h] Fix flash write temp file access on Windows (#68)

* [ln882h] reduce transfer baudrate to improve reliability

* fix ln882x flash write on Windows platform

* black reformat

Author: lamauny

ltchiptool/soc/ln882h/util/ln882htool.py

@@ -207,18 +207,17 @@ def flash_write(
         self.command(f"startaddr 0x{offset:X}")
 
         # Convert stream to temporary file before sending with YMODEM
-        tmp_file = NamedTemporaryFile()
-        with open(tmp_file.name, "wb") as f:
+        with NamedTemporaryFile(delete=False) as f:
             f.write(stream.getbuffer())
 
-            self.command(f"upgrade", waitresp=False)
+        self.command(f"upgrade", waitresp=False)
 
-            self.push_timeout(3)
-            debug(f"YMODEM: transmitting to 0x{offset:X}")
-            if not self.ym.send([f.name], callback=callback):
-                self.change_baudrate(prev_baudrate)
-                self.pop_timeout()
-                raise RuntimeError("YMODEM transmission failed")
+        self.push_timeout(3)
+        debug(f"YMODEM: transmitting to 0x{offset:X}")
+        if not self.ym.send([f.name], callback=callback):
+            self.change_baudrate(prev_baudrate)
+            self.pop_timeout()
+            raise RuntimeError("YMODEM transmission failed")
 
         self.link()