Bluetooth: 6LoWPAN: add missing hci_dev_put() in get_l2cap_conn()

stable inclusion
from stable-v5.10.159
commit 1717354d77f82c733ff5e828b897f3b1a7053d6d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7NTXH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1717354d77f82c733ff5e828b897f3b1a7053d6d



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[ Upstream commit 747da130 ]

hci_get_route() takes reference, we should use hci_dev_put() to release
it when not need anymore.

Fixes: 6b8d4a6a ("Bluetooth: 6LoWPAN: Use connected oriented channel instead of fixed one")
Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>