Fix kretprobe multi attachement
Fix kretprobe multi attachement

Commit b09df8e20ac279cfcdadb56f19484d18ed527716 made a mistake in
setting a kprobe_multi flag for kretprobes.

Fixes: b09df8e20ac279cfcdadb56f19484d18ed527716

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace