Process receive event from same process by default. Add a flag to be
able to receive event from all processes, this requires super user
permission.

Event using pid 0 to send the event to all processes, to keep the
default behavior of existing SMI events.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>