清理Makefile冗余项，各模块Makefile里不需要再次引用公共路径，只需引用私有头文件路径

close: #I49MOO
Signed-off-by: Narvinzzz <zhaotianyu9@huawei.com>
Change-Id: I2dd7189c866498896461f78bfed5444ae1d86876

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 new
        version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP

Change-Id: Ia6c1f6302407a707b3ec9b805f4c92d8a7970b86