ARM: mach-shmobile: r8a7740: add INTC support

R8A7740 GIC can not get external IRQx interrupt directly
without GIC - INTC demux support.

Current AG5 is using GIC - INTCS demux with
special irq relocation. but GIC - INTCA demux
is still not supported and it needs irq number re-mapping.

OTOH, normal INTC support as before is very enough for R8A7740,
because it is not SMP CPU.
This patch adds INTCA/INTCS support instead of GIC.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>