x86: Skip APIC-access address tests beyond mapped RAM

We no longer have any tests in vmx_tests.c that use
xfail_beyond_mapped_ram. However, an upcoming change to kvm will exit
to userspace with a kvm internal error whenever launching a nested VM
with the vmcs12 APIC-access address set to a non-cacheable address in
L1. Reuse the xfail_beyond_mapped_ram plumbing to support
skip_beyond_mapped_ram, and skip any APIC-access address tests that
use addresses beyond mapped RAM, so that the test won't induce a kvm
internal error.

Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>