MIPS: Alchemy: update cpu feature overrides

No advanced MIPS features for Alchemy.
This patch shaves additional 43kB off the DB1300 kernel
(~0.5% size reduction).

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15286/


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