Revert "arm/kernel: fix merge error"

This reverts commit 18f2a28322a196162f70fcbe89bc331c74f8c959.
Revert "sched: Cleanup cpu_active madness"

This reverts commit 5607778a3ccc6f7b2e4354810e161d691056abcb.
Revert "ARM: 6998/2: kernel: use proper memory barriers for bitops"

This reverts commit 56e679b0992f37231c1c7b1382e608dc03b8999f.