sparc64: Make smp_cross_call_masked() take a cpumask_t pointer.

Ideally this could be simplified further such that we could pass
the pointer down directly into the xcall_deliver() implementation.

But if we do that we need to do the "cpu_online(cpu)" and
"cpu != self" checks down in those functions.

Signed-off-by: David S. Miller <davem@davemloft.net>