sparc64: Use CPU_POKE to resume idle cpu

Use CPU_POKE hypervisor call to resume idle cpu if supported.

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>