cpu: Add support for microcode version and CPU ID

Some CPUs use microcode and each core can have a different version of
microcode loaded. Also some CPUs support the concept of an integer ID used
for identification purposes. Add support for these in the CPU uclass.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>