sched: use a 2-d bitmap for searching lowest-pri CPU

sched: use a 2-d bitmap for searching lowest-pri CPU

The current code use a linear algorithm which causes scaling issues
on larger SMP machines.  This patch replaces that algorithm with a
2-dimensional bitmap to reduce latencies in the wake-up path.

Signed-off-by: Gregory Haskins <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>