Introduce invalid_phys_cpuid() to identify cpu with invalid
physical ID, then used it as replacement of the direct comparisons
with PHYS_CPUID_INVALID.
Signed-off-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>