[POWERPC] Fix audit syscall success/failure reporting on PowerPC

Due to my stupidity, we were checking for the wrong bit in CCR when
attempting to determine whether a syscall succeeded or not. Remedy the
symptom, if not the cause.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>