[PATCH] Add macros for rdtscp

This patch adds macros for reading tsc via the RDTSCP instruction, as well
as writing the auxilliary MSR read by RDTSCP to msr.h

[AK: changed rdtscp definition for old binutils]

Signed-off-by: Vojtech Pavlik <vojtech@suse.cz>
Signed-off-by: Andi Kleen <ak@suse.de>