ppc: Batch TLB flushes on 32-bit 6xx/7xx/7xxx in hash mode

ppc: Batch TLB flushes on 32-bit 6xx/7xx/7xxx in hash mode

This ports the existing 64-bit mechanism to 32-bit, thus series
of 64 tlbie's followed by a sync like some versions of Darwin
(ab)use will result in a single flush.

We apply a pending flush on any sync instruction though, as Darwin
doesn't use tlbsync on non-SMP systems.

Signed-off-by: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: David Gibson <[email protected]>