This config option doesn't exist any more, remove the leftover code
for it too.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5302/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>