MIPS: Alchemy: move commandline mangling out of common code

Not every alchemy-based board might want these options forced on it,
and most of this stuff seems to be intended for devboard code anyway.
Remove commandline mangling code out of common chip code and instead
add relevant sections to all in-tree boards to not change existing
behaviour.

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