arch: arm: use dt and UCLASS_IRQ to get gic details

Use device tree and UCLASS_IRQ driver to get following
Generic Interrupt Controller (GIC) details,

-GIC Distributor interface (GICD) base address and
-GIC Redistributors (GICR) base address.

Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Reviewed-by: Simon Glass <sjg@chromium.org>