frv: fix the broken preempt

Just get %icc2 into the state we would have after local_irq_disable()
and physical IRQ having happened since then.  Then we can simply
use preempt_schedule_irq() and be done with the whole mess.

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>