Bluetooth: Fix use-after-free in hci_remove_ltk/hci_remove_irk

Similar to commit 0f7d9b31

 ("netfilter: nf_tables: fix use-after-free
in nft_set_catchall_destroy()"). We can not access k after kfree_rcu()
call.

Cc: stable@vger.kernel.org
Signed-off-by: Min Li <lm0963hack@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>