drivers: gicv3: Add Support for Extended SPI

Added support to gicv3 driver to utilize the
extended SPI MMIO registers introduced in
GICv3.1 for the extended SPI range.

Documentation for the Extended Shared
Peripheral Interrupts extension can be found
in the ARM General Interrupt Controller
Architecture Specification:

https://developer.arm.com/documentation/ihi0069/latest/



Signed-off-by: Adam Openshaw <quic_adamo@quicinc.com>