This config option never really worked, and has bit-rotted to the
point of being completely useless. Remove it completely.

Signed-off-by: David Daney
Cc: James Hogan
Cc: Steven J. Hill
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15314/
Signed-off-by: Ralf Baechle