x86: entry_64.S: rename

Impact: cleanup

Rename:

   CFI_PUSHQ  =>  pushq_cfi
   CFI_POPQ   =>  popq_cfi
   CFI_MOVQ   =>  movq_cfi

To make it blend better into regular assembly code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>