x86: Update the MP constants to avoid conflicts

x86: Update the MP constants to avoid conflicts

These constants conflict with error codes returned by the MP
implementation when something is wrong. In particular, mp_first_cpu()
returns MP_SELECT_BSP when running without multiprocessing enabled.
Since this is -2, it is interpreted as an error by callers, which
expect a positive CPU number for the first CPU.

Correct this by using a different range for the pre-defined CPU
numbers, above zero and out of the range of possible CPU values. For
now it is safe to assume there are no more than 64K CPUs.

This fixes the 'mtrr' command when CONFIG_SMP is not enabled.

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