1, this RomFS's codebase is Nuttx romfs, then it is compatible with
   Linux RomFS and you can create such a file system using the tool
   genromfs.
2, there are two major changes against with the original Nuttx romfs:
   1), it is memory-based: all contents of the fs are stored in the
       memory in the very first stage of "mount".
   2), this version of romfs is altered to be compatible with our
       version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP