x86-64, doc: Remove int 0xcc from entry_64.S documentation

Commit 3ae36655b97a03fa1decf72f04078ef945647c1a (x86-64: Rework vsyscall
emulation and add vsyscall= parameter) removed the special use of the
0xcc IDT vector.

Remove it from Documentation/x86/entry_64.txt also.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Acked-by: Andy Lutomirski <luto@MIT.EDU>
Link: http://lkml.kernel.org/r/1313447210-9149-1-git-send-email-cesarb@cesarb.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

Documentation/x86/entry_64.txt

@@ -27,9 +27,6 @@ Some of these entries are:
    magically-generated functions that make their way to do_IRQ with
    the interrupt number as a parameter.
 
- - emulate_vsyscall: int 0xcc, a special non-ABI entry used by
-   vsyscall emulation.
-
  - APIC interrupts: Various special-purpose interrupts for things
    like TLB shootdown.