arm_gic: Update ID registers based on revision

arm_gic: Update ID registers based on revision

Update the GIC ID registers (registers above 0xfe0) based on the GIC
revision instead of using the sames values for all GIC implementations.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Tested-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Message-id: 629e7fa5d47f2800e51cc1f18d12635f1eece349.1453333840.git.alistair.francis@xilinx.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>