fs: use menuconfig to control the Misc. filesystems menu

Have one option to control Miscellaneous filesystems.  This makes it easy
to disable all of them at one time.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>