Currently both the tlbiva instruction (used on 44x chips) and the tlbie
instruction (used on hash MMU chips) are both handled via
ppc_tlb_invalidate_one().  This is silly, because they're invoked from
different places, and do different things.

Clean this up by separating out the tlbiva instruction into its own
handling.  In fact the implementation is only a stub anyway.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Alexander Graf <agraf@suse.de>