sdt: Tear down probes in kernel modules during kldunload

Previously only providers in kernel modules were removed leaving
dangling pointers to tracepoints, etc. in unloaded kernel modules.

PR: 281825
Reported by: Sony Arpita Das <sonyarpitad@chelsio.com>
Reviewed by: markj
Fixes: ddf0ed09bd8f sdt: Implement SDT probes using hot-patching
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D46890