sh: Convert INTC2 to IRQ table registration.

Currently the INTC2 code contains a fixed IRQ table that it
iterates through to set the handler type, we move this in to
the CPU subtype setup code instead and allow for submitting
the table that way.

This drops the ST40 tables, as nothing has been happening
with those processors, while converting the only existing
users to use the new table directly (SH7760 and SH7780).

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