mtd: sh_flctl: Expand FLCMNCR register bit field

Add support for a new hardware generation. The meaning of some bits
of the FLCMNCR register changed, so some new defines are added
parallel to the existing ones to keep backward compatibility.

The defines allow to choose an appropriate clocking scheme.

Signed-off-by: Bastian Hecht <hechtb@gmail.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>