MIPS: Invalidate old TLB mappings when updating huge page PTEs.

Without this, stale Icache or TLB entries may be used.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
https://patchwork.linux-mips.org/patch/2318/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>