Merge changes from topic "bk/gicv5_full"

* changes:
  feat(realm): set the PMU IRQ number depending on GIC version
  feat(fvp): set the timer IRQ number depending on GIC version
  refactor(gic): defer IRQ handler management to the GIC driver
  refactor(gic): make the concept of SGI generic
  feat(gicv5): add a GICv5 driver
  feat(gicv5): add GICv5 instructions and register accessors