x86: trampoline_64.S - use predefined constants with simplification

Impact: cleanup

We may use macros from processor-flags.h instead
of hardcoding bits. Actually it's not direct mapping
of old instructions with new ones -- BTS does change
CF flag while MOV does not. But i didn't find any
dependency on CF in this code.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>