On SH7709S, DMAC can be found at 0xa4000020 (as with most of
the other sh3 cpu subtypes).

Split out definition of DMAC base address from definitions of
DMTE irqs.
Signed-off-by: NSteve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>