Revert "Fix memory leak in sowtware multiplex events (sw_multiplex.c)"
Revert "Fix memory leak in sowtware multiplex events (sw_multiplex.c)"

This commit corrupted the MPX event linked list and
causes, among other things, the sdsc4-mpx test to fail.

This reverts commit 8891be9a2e97482dbe2201fd6c601bd805dde26f.

pyrovski/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,pyrovski/papi,pyrovski/papi,pyrovski/papi,pyrovski/papi