mm: bank-aware allocation performance improvement

Move bitmap creation to the cgroup interface instead of
doing it over and over again in the critical path of
__rmqueue_smallest()

Results with 433.milc (test load, 230,000 page allocs)

Per-page average latency differences:

	Before: 1351 ns (total 310 ms = 4.13 %)
	 After:  359 ns (total  82 ms = 1.10 %)
	 Buddy:   25 ns (total   5 ms = 0.07 %)
mm: deterministic bank interleaving

Instead of being random, it iterate all allowed banks
one-by-one. More reliable and shows better performance (even compared
to the stock buddy algorithm)