tracing/fprobe: Unregister fprobe even if memory allocation fails

tracing/fprobe: Unregister fprobe even if memory allocation fails

unregister_fprobe() can fail under memory pressure because of memory
allocation failure, but this maybe called from module unloading, and
usually there is no way to retry it. Moreover. trace_fprobe does not
check the return value.

To fix this problem, unregister fprobe and fprobe_hash_node even if
working memory allocation fails.
Anyway, if the last fprobe is removed, the filter will be freed.

Link: https://lore.kernel.org/all/177669365629.132053.8433032896213721288.stgit@mhiramat.tok.corp.google.com/
Fixes: 4346ba160409 ("fprobe: Rewrite fprobe on function-graph tracer")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>