MIPS: Alchemy: provide cpu feature overrides.

Add cpu feature override constants tailored for all Alchemy variants
currently in existence.

Signed-off-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

 create mode 100644 arch/mips/include/asm/mach-au1x00/cpu-feature-overrides.h