sh: remove old broken pint code

The code in arch/sh/kernel/cpu/irq/pint.c doesn't compile, so let's
get rid of it to make space for a future pint implementation on top
of intc.

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