The last git import created a dependency on pm_power_down. Borrowing from
ARM the following patch provides definitions of the needed variables in
order for kernels to link.
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
@@ -41,6 +41,15 @@
+ * The following aren't currently used.
* The idle thread. There's no useful work to be done, so just try to conserve
* power and have a low exit latency (ie sit in a loop waiting for somebody to
* say that they'd like to reschedule)