ARM: dts: keystone: Add the GICV and GICH address space

Update the Keystone gic node to add the GICV and GIGH address space
needed by the KVM.

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>