[MTD] generalise the handling of MTD-specific superblocks

Generalise the handling of MTD-specific superblocks so that JFFS2 and ROMFS
can both share it.

Signed-off-by: David Howells <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>
5 files changed