x86: add CLBR_ defines for 64-bit

x86_64 needs a potentially larger clobber list than i386, due to its calling
convention. So we add more CLBR_ defines for it.
Note that CLBR_ANY is different for each of the architectures, since it comprises
the notion of "All call clobbers in this architecture"

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>