Move declarations of bsp_interrupt_get_affinity() and
bsp_interrupt_set_affinity() to <bsp/irq-generic.h>. Canonicalize the
<bsp/irq.h> includes.
Implement bsp_interrupt_get_affinity() and bsp_interrupt_set_affinity() only if
needed (usually RTEMS_SMP).
Provide stub implementations for i386 to fix build errors.
Restrict the affinity set to the set of online processors. Make sure
the affinity set for an interrupt vector contains at least one online
processor.
Update #3269.