ports: Use vfs module instead of os.

Signed-off-by: Damien George <damien@micropython.org>

ports/esp8266/boards/ESP8266_GENERIC/board.md

@@ -13,7 +13,7 @@ Note: v1.12-334 and newer (including v1.13) require an ESP8266 module with
 2MiB of flash or more, and use littlefs as the filesystem by default.  When
 upgrading from older firmware please backup your files first, and either
 erase all flash before upgrading, or after upgrading execute
-`os.VfsLfs2.mkfs(bdev)`.
+`vfs.VfsLfs2.mkfs(bdev)`.
 
 ### OTA builds
 Over-The-Air (OTA) builds of the ESP8266 firmware are also provided.

ports/esp8266/modules/_boot.py

@@ -1,12 +1,12 @@
 import gc
 
 gc.threshold((gc.mem_free() + gc.mem_alloc()) // 4)
-import os
+import vfs
 from flashbdev import bdev
 
 if bdev:
     try:
-        os.mount(bdev, "/")
+        vfs.mount(bdev, "/")
     except:
         import inisetup
 

ports/esp8266/modules/inisetup.py

@@ -1,4 +1,4 @@
-import os
+import vfs
 import network
 from flashbdev import bdev
 
@@ -36,7 +36,7 @@ def fs_corrupted():
             """\
 The filesystem starting at sector %d with size %d sectors looks corrupt.
 You may want to make a flash snapshot and try to recover it. Otherwise,
-format it with os.VfsLfs2.mkfs(bdev), or completely erase the flash and
+format it with vfs.VfsLfs2.mkfs(bdev), or completely erase the flash and
 reprogram MicroPython.
 """
             % (bdev.start_sec, bdev.blocks)
@@ -48,9 +48,9 @@ def setup():
     check_bootsec()
     print("Performing initial setup")
     wifi()
-    os.VfsLfs2.mkfs(bdev)
-    vfs = os.VfsLfs2(bdev)
-    os.mount(vfs, "/")
+    vfs.VfsLfs2.mkfs(bdev)
+    fs = vfs.VfsLfs2(bdev)
+    vfs.mount(fs, "/")
     with open("boot.py", "w") as f:
         f.write(
             """\