MFC 284175:

MFC 284175:
Handle X2APIC entries in the MADT for APICs with an ID < 255.  At least one
BIOS has been seen to include such entries even though the relevant specs
require that X2APIC entries only be used for CPUs with an APIC ID >= 255.

This was tested on a system with "plain" local APIC entries in the MADT
to ensure no regressions, but it has not yet been tested on a system with
X2APIC entries in the MADT.  Currently such systems do not boot at all,
and with this change they might now boot correctly.

git-svn-id: svn://svn.freebsd.org/base/stable/10@288461 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f