inst->handles is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of knav_dev_lock.

Hence, add corresponding lockdep expression to silence false-positive
lockdep warnings, and harden RCU lists.

Add macro for the corresponding lockdep expression.

Link: https://lore.kernel.org/r/20200118042433.4968-1-frextrite@gmail.comSigned-off-by: Amol Grover <frextrite@gmail.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Olof Johansson <olof@lixom.net>