Revert "devlink: Remove not-executed trap group notifications"

This reverts commit 8bbeed48 as it
revealed that mlxsw and netdevsim (copy/paste from mlxsw) reregisters
devlink objects during another devlink user triggered command.

Fixes: 22849b5e

 ("devlink: Remove not-executed trap policer notifications")
Reported-by:  <syzbot+93d5accfaefceedf43c1@syzkaller.appspotmail.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>