[PATCH] x86_64: Don't do syscall exit tracing twice

This fixes a regression from the earlier DOS fix for non canonical
IRET addresses. It broke UML.

int_ret_from_syscall already does syscall exit tracing, so
no need to do it again in the caller.

This caused problems for UML and some other special programs doing
syscall interception.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>