hw/arm/bcm2836: Create proper bcm2837 device

hw/arm/bcm2836: Create proper bcm2837 device

The bcm2837 is pretty similar to the bcm2836, but it does have
some differences. Notably, the MPIDR affinity aff1 values it
sets for the CPUs are 0x0, rather than the 0xf that the bcm2836
uses, and if this is wrong Linux will not boot.

Rather than trying to have one device with properties that
configure it differently for the two cases, create two
separate QOM devices for the two SoCs. We use the same approach
as hw/arm/aspeed_soc.c and share code and have a data table
that might differ per-SoC. For the moment the two types don't
actually have different behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180313153458.26822-7-peter.maydell@linaro.org