TetherController - remove bpf dump code

There's bpf map dumping code in the Tethering mainline module.
Additionally we don't want netd to have access to the tethering maps.

Test: atest, TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ia6abe3cadcbb32a1a94cbeef26ed8957e09e60ab