KVM: nVMX: move host EFER consistency checks to VMFail path

Invalid host state related to loading EFER on VMExit causes a
VMFail(VMXERR_ENTRY_INVALID_HOST_STATE_FIELD), not a VMExit.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>