SPARC/LEON: added support for IRQAMP IRQ Controller

Needed for LEON AMP systems where different CPUs are routed to

different IRQ controllers. This patch selects the IRQ Controller
which has been routed to the boot CPU, it is up to the boot loader
to configure the IRQ controller.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>