MIPS: tlb-r4k: Add missing HTW stop/start sequences

MIPS: tlb-r4k: Add missing HTW stop/start sequences

commit 6a8dff6ab16c903b0d8ef5fbf21543f39bf5d675 upstream.

HTW needs to stop and start again whenever the EntryHI register
changes otherwise an inflight HTW operation might use the new
EntryHI register for updating an old entry and that could lead
to crashes or even a machine check exception. We fix this by
ensuring the HTW has stop whenever the EntryHI register is about
to change

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8511/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>