sh: Support CPU affinity masks for INTC controllers.

This hooks up the ->set_affinity() for the INTC controllers, which can be
done as just a simple copy of the cpumask. The enable/disable paths
already handle SMP register strides, so we just test the affinity mask in
these paths to determine which strides to skip over.

The early enable/disable path happens prior to the IRQs being registered,
so we have no affinity mask established at that point, in which case we
just default to CPU_MASK_ALL. This is left as it is to permit the force
enable/disable code to retain existing semantics.

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