[20/25] stack::l2cap Use stack::l2cap::get_interface() am: fe338f83 am: 1c5f0bc4

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/3254846



Change-Id: Ic350b64a484abdfc55824812099625a3a8d7d172
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>