sh64: Wire up the shared __flush_xxx_region() flushers.

Now with all of the prep work out of the way, kill off the SH-5 variants
and use the SH-4 version directly. This also takes advantage of the
unrolling that was previously done for the new version.

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

diff --cc arch/sh/mm/Makefile_64
Simple merge

diff --cc arch/sh/mm/cache-sh5.c
Simple merge