MIPS: Alchemy: remove unused board headers

The information in those headers is no longer necessary.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2876/


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