MIPS: Alchemy: Fix up PM code on Au1550/Au1200

Au1550/Au1200 have a different memory controller which requires additi-
onal code to properly put memory to sleep (code taken from AMD/RMI's
Linux-2.6.11 source package).

Also fix up the remaining pm-related paths to compile on Au1200/Au1550
platforms.

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