sh: Annotate irq functions with "notrace"

Now that SH's irqflags functions are out of line it becomes necessary to
mark them as "notrace" so that we don't try to trace them.

[ Do the same for irq_64.c -- PFM. ]

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>