mtd: Handle compat ioctls directly; remove all trace from compat_ioctl.c

Remove all references to MTD ioctls from fs/compat_ioctl.c and let
them all be handled by mtd_compat_ioctl().

Signed-off-by: Kevin Cernekee <kpc.mtd@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>