ARM: Fix issue with with way MPIDR is read to include affinity levels.

The simple_bootloader checks for CPU0 in a manner incompatible with systems
actually using affinity levels -- just looking at MPIDR[7:0]. However, in
future we may wish to use real affinity levels and this method will be in danger
of matching several CPUs with affinity0 = 0.

Match affinity2 == affinity1 == affinity0 == 0 instead.

ARM: Add support for Versatile Express extended memory map

Also clean up how we create boot loader memory a bit.

ARM: Boot loader changes that make it more flexible about load and I/O addrs

ARM: Add code for a simple bootloader for MP boot.