ARM: shmobile: r8a73a4 IRQC support V2

Add IRQC interrupt controller support to r8a73a4 by
hooking up two IRQC instances to handle 58 external
IRQ signals. There IRQC controllers are tied to SPIs
of the GIC. On r8a73a4 exact IRQ pin routing is handled
by the PFC which is excluded from this patch.

Both platform devices and DT devices are added in this
patch. The platform device versions are used to provide
a static interrupt map configuration for board code
written in C.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>