x86/vmx: Fixup removals of MSR load/save list entries

x86/vmx: Fixup removals of MSR load/save list entries

Commit 540d5422 ("x86/vmx: Support removing MSRs from the host/guest
load/save lists") introduced infrastructure finally exposed by
commit fd32dcfe ("x86/vmx: Don't leak EFER.NXE into guest context")
that led to a functional regression on Harpertown and earlier cores
(Gen 1 VT-x) due to MSR count being incorrectly set in VMCS.
As the result, as soon as guest EFER becomes equal to Xen EFER
(which eventually happens in almost every 64-bit VM) and its MSR
entry is supposed to be removed, a stale version of EFER is loaded
into a guest instead causing almost immediate guest failure.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>