[MIPS] Alchemy: kill useless #include's, #define's and extern's

Go thru the Alchemy code and hunt down every unneeded #include, #define, and
extern (some of which refer to already long dead functions).

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>