x86: introduce is_pv_64bit_{vcpu,domain}

x86: introduce is_pv_64bit_{vcpu,domain}

This is useful to rewrite the following pattern (v is PV vcpu)

   if ( is_pv_32bit_vcpu(v) )
       do_foo;
   else
       do_bar;

to

   if ( is_pv_32bit_vcpu(v) )
       do_foo;
   else if ( is_pv_64bit_vcpu(v) )
       do_bar;
   else
       ASSERT_UNREACHABLE;
.

Previously it is not possible to rely on DCE to eliminate the do_bar
part. It becomes possible with the new code structure.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>