Revert "cpu: Fix generic idle thread allocation"

This reverts commit 82265b7a017eb7df20f6e67d708b51e3f3664020.
Revert "smp: Add task_struct argument to __cpu_up()"

This reverts commit 7adbc69cd962d0721d217d622f52fb288597bc08.

Conflicts:
	arch/arm/kernel/smp.c