Add base support for implementing platform_irq_to_vector(), and
then use it on SN2.
Signed-off-by: NKenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Acked-by: NJohn Keller <jpk@sgi.com>
Signed-off-by: NTony Luck <tony.luck@intel.com>