MIPS: features: Add initial support for TLBINVF capable cores

New Aptiv cores support the TLBINVF instruction for flushing
the VTLB.

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6130/