kvm: nVMX: Fix nested_vmx_check_msr_bitmap_controls

Allow the L1 guest to specify the last page of addressable guest
physical memory for an L2 MSR permission bitmap. Also remove the
vmcs12_read_any() check that should never fail.

Fixes: 3af18d9c ("KVM: nVMX: Prepare for using hardware MSR bitmap")
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>