sh: Add support for SH7206 and SH7619 CPU subtypes.

This implements initial support for the SH7206 (SH-2A) and SH7619
(SH-2) MMU-less CPUs.

Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>