irqchip/gic-v3: Describe the SGI range

As we are about to start making use of SGIs in a more conventional
way, let's describe it is the GICv3 list of interrupt types.

Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
1 file changed