fs: Kill sh dependency for binfmt_flat.

fs: Kill sh dependency for binfmt_flat.

Not really sure where this bogosity came from, but there's certainly
nothing special about sh that lets us use flat files with the MMU on.

Kill the dependency, and leave it as !MMU, like it is for all of the
other nommu-wielding ports.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>