arm: lib: Add GICV2 driver

arm: lib: Add GICV2 driver

Add a generic GICV2 driver that:
- parses the DT and generates the ACPI MADT subtables
- implement of_xlate() and allows irq_get_by_index() to return the
  correct interrupt mappings

Map DT interrupts to ARM GIC interrupts	as follows:

- Interrupt numbers ID32-ID1019 are used for SPIs
- ID0-ID15 are used for SGIs
- ID16-ID31 are used for PPIs

TEST: Booted on QEMU raspb4 using GICV2 driver model generated MADT.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Simon Glass <sjg@chromium.org>