Updated links to Mbed OS

Author: geky

README.md

@@ -141,10 +141,11 @@ make test
 
 ## Related projects
 
-[mbed-littlefs](https://github.com/armmbed/mbed-littlefs) - The easiest way to
-get started with littlefs is to jump into [mbed](https://os.mbed.com/), which
-already has block device drivers for most forms of embedded storage. The
-mbed-littlefs provides the mbed wrapper for littlefs.
+[Mbed OS](https://github.com/ARMmbed/mbed-os/tree/master/features/filesystem/littlefs) -
+The easiest way to get started with littlefs is to jump into [Mbed](https://os.mbed.com/),
+which already has block device drivers for most forms of embedded storage. The
+littlefs is available in Mbed OS as the [LittleFileSystem](https://os.mbed.com/docs/latest/reference/littlefilesystem.html)
+class.
 
 [littlefs-fuse](https://github.com/geky/littlefs-fuse) - A [FUSE](https://github.com/libfuse/libfuse)
 wrapper for littlefs. The project allows you to mount littlefs directly in a