Receive available and used space from JFFS2

[Andrew Lunn]

> I've noticed that you used a 32 bit value for returning fs space info, 
> this may
> not be such an good idea - check an old discussion about this at
> http://ecos.sourceware.org/ml/ecos-devel/2003-07/msg00031.html .
> I think a better way would be to return a structure with free/used space
> in blocks + block size.

You are assuming a block based storage media. romfs does not have
blocks. Although jffs2 uses flash blocks, the files themselves are not
block based. Only ramfs and fat use blocks.

I think i might change the interface to pass a cyg_uint64 instead.

> It would also be nice to put the keys (+ common structures)
> in a separate file - like it is done with IO config_keys.h.

Humm. I think Nick put the origional 3 keys in fileio.h. He should
decide if they should be moved out to a seperate header file.

        Andrew