hw/arm/bcm2836: Make the SoC code modular

hw/arm/bcm2836: Make the SoC code modular

This file creates the BCM2836/BCM2837 blocks.
The biggest differences with the BCM2838 we are going to add, are
the base addresses of the interrupt controller and the peripherals.
Add these addresses in the BCM283XInfo structure to make this
block more modular. Remove the MCORE_OFFSET offset as it is
not useful and rather confusing.

Reviewed-by: Esteban Bosse <estebanbosse@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20191019234715.25750-6-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>