sh: no high level trigger on some sh3 cpus

The processor models sh7706, sh7707 and sh7709 don't support high
level trigger sense configuration. And the intc code looks like
crap these days so what's the difference.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>