sh: hd64461 tidying.

Kill off the hd64461 io.c, as all of the hd64461 users are now
using the generic I/O routines.

[ hd64461/ moved to hd64461.c by Paul ]

Signed-off-by: Kristoffer Ericson <kristoffer.ericson@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>