Add architectural definitions and probing for the MIPS Common Device
Memory Map (CDMM) region. When supported and enabled at a particular
physical address, this region allows some number of per-CPU devices to
be discovered and controlled via MMIO.
A bit exists in Config3 to determine whether the feature is present, and
a CDMMBase CP0 register allows the region to be enabled at a particular
physical address.
[ralf@linux-mips.org: Sort conflict with other patches.]