esp32/moduos: Enable uos.VfsLfs2 for littlefs filesystems.

This commit adds support for littlefs (v2) on all esp32 boards.

The original FAT filesystem still works and any board with a preexisting
FAT filesystem will still work as normal.  It's possible to switch to
littlefs by reformatting the block device using:

    import uos, flashbdev
    uos.VfsLfs2.mkfs(flashbdev.bdev)

Then when the board reboots (soft or hard) the new littlefs filesystem will
be mounted.  It's possible to switch back to a FAT filesystem by formatting
with uos.VfsFat.mkfs(flashbdev.bdev).

ports/esp32/Makefile

@@ -31,6 +31,7 @@ MICROPY_PY_USSL = 0
 MICROPY_SSL_AXTLS = 0
 MICROPY_FATFS = 1
 MICROPY_PY_BTREE = 1
+MICROPY_VFS_LFS2 = 1
 
 FROZEN_MANIFEST ?= boards/manifest.py
 

ports/esp32/moduos.c

@@ -38,6 +38,7 @@
 #include "extmod/misc.h"
 #include "extmod/vfs.h"
 #include "extmod/vfs_fat.h"
+#include "extmod/vfs_lfs.h"
 #include "genhdr/mpversion.h"
 
 extern const mp_obj_type_t mp_fat_vfs_type;
@@ -123,6 +124,12 @@ STATIC const mp_rom_map_elem_t os_module_globals_table[] = {
     #if MICROPY_VFS_FAT
     { MP_ROM_QSTR(MP_QSTR_VfsFat), MP_ROM_PTR(&mp_fat_vfs_type) },
     #endif
+    #if MICROPY_VFS_LFS1
+    { MP_ROM_QSTR(MP_QSTR_VfsLfs1), MP_ROM_PTR(&mp_type_vfs_lfs1) },
+    #endif
+    #if MICROPY_VFS_LFS2
+    { MP_ROM_QSTR(MP_QSTR_VfsLfs2), MP_ROM_PTR(&mp_type_vfs_lfs2) },
+    #endif
     #endif
 };