irqchip/gic: Store GIC configuration parameters

Store the GIC configuration parameters in the GIC chip data structure.
This will allow us to simplify the code by reducing the number of
parameters passed between functions.

Update the __gic_init_bases() function so that we only need to pass a
pointer to the GIC chip data structure and no longer need to pass the
GIC index in order to look-up the chip data.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>