x86/vmx: Revert "VMX: use a single, global APIC access page"

x86/vmx: Revert "VMX: use a single, global APIC access page"

The claim "No accesses would ever go to this page." is false.  A consequence
of how Intel's APIC Acceleration works, and Xen's choice to have per-domain
P2Ms (rather than per-vCPU P2Ms) means that the APIC page is fully read-write
to any vCPU which is not in xAPIC mode.

This reverts commit 58850b9074d3e7affdf3bc94c84e417ecfa4d165.

This is XSA-412 / CVE-2022-42327.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>