sched: get rid of boutique sched.c allocations, use cpumask_var_t.

Impact: use new general API

Using lots of allocs rather than one big alloc is less efficient, but
who cares for this setup function?

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

Signed-off-by: Ingo Molnar <mingo@elte.hu>