perf: Change the is_software_event() definition

The is_software_event() definition always confuses me because its an
exclusive expression, make it an inclusive one.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>