selftests/bpf: fix uprobe.path leak in bpf_testmod

testmod_unregister_uprobe() forgets to path_put(&uprobe.path).

Signed-off-by: Jiri Olsa <olsajiri@gmail.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240801132724.GA8791@redhat.com