powerpc/e6500: hw tablewalk: clear TID in kernel indirect entries

powerpc/e6500: hw tablewalk: clear TID in kernel indirect entries

Previously TID was being cleared before the tlbsx, but not after.  This
can lead to a multiway hit between a TLB entry with TID=0 (previously
inserted when PID=0) and a TLB entry with TID!=0 that matches PID.
This can theoretically result in undefined behavior, though we probably
get lucky due to the details of the overlap.  It also results in the
inability to use multihit detection to detect other conflicting TLB
entries, as well as poorer TLB utilization due to duplicating kernel
TLB entries.

Rather than try to patch up MAS1 after tlbsx, the entire value is
saved/restored as with MAS2.

I observed a slight improvement in TLB miss performance with this patch
applied.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Reported-by: Ed Swarthout <ed.swarthout@freescale.com>