powerpc/tm: Update cause codes documentation

Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> # 3.9 only
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Documentation/powerpc/transactional_memory.txt

@@ -155,6 +155,7 @@ These are defined in <asm/reg.h>, and distinguish different reasons why the
 kernel aborted a transaction:
 
  TM_CAUSE_RESCHED       Thread was rescheduled.
+ TM_CAUSE_TLBI          Software TLB invalide.
  TM_CAUSE_FAC_UNAV      FP/VEC/VSX unavailable trap.
  TM_CAUSE_SYSCALL       Currently unused; future syscalls that must abort
                         transactions for consistency will use this.