sparc64: Add a new hypercall CPU_POKE

This adds a new hypercall CPU_POKE for quickly waking up an idle CPU.
CPU_POKE should only be sent to valid non-local CPUs.

Signed-off-by: Rob Gardner <rob.gardner@oracle.com>
Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
Reviewed-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>