tracing: fprobe: Cleanup fprobe hash when module unloading

Cleanup fprobe address hash table on module unloading because the
target symbols will be disappeared when unloading module and not
sure the same symbol is mapped on the same address.

Note that this is at least disables the fprobes if a part of target
symbols on the unloaded modules. Unlike kprobes, fprobe does not
re-enable the probe point by itself. To do that, the caller should
take care register/unregister fprobe when loading/unloading modules.
This simplifies the fprobe state managememt related to the module
loading/unloading.

Link: https://lore.kernel.org/all/174343534473.843280.13988101014957210732.stgit@devnote2/



Fixes: 4346ba16 ("fprobe: Rewrite fprobe on function-graph tracer")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>