x86/64: Fix syscall return code when ptrace or audit is active

x86/64: Fix syscall return code when ptrace or audit is active

Fix the return value from the 64-bit kernel when you call with a bad
system call number with tracing enabled (for either ptrace or audit).
What should happen is that the user process gets a -ENOSYS return
call from the syscall; what actually happens (only in the 64-bit
kernel) is that you get back the system call number. The 32-bit
kernel does not suffer from this bug.

Signed-off-by: Chris Lalancette <clalance@redhat.com>