esp32/modules: On initial setup mount internal flash at root.

Like it's done on normal boot up.  Fixes issue #5004.

ports/esp32/modules/inisetup.py

@@ -29,8 +29,7 @@ def setup():
     print("Performing initial setup")
     uos.VfsFat.mkfs(bdev)
     vfs = uos.VfsFat(bdev)
-    uos.mount(vfs, '/flash')
+    uos.mount(vfs, '/')
-    uos.chdir('/flash')
     with open("boot.py", "w") as f:
         f.write("""\
 # This file is executed on every boot (including wake-boot from deepsleep)