This is a fix for issue with id 746-001125: Tanaro: Bluetooth does not work

This is a cherry-pick of the following commit:
commit 72354854
Author: Pavel Skripkin <paskripkin@gmail.com>
Date:   Sun Mar 13 20:49:36 2022 +0300

    Bluetooth: hci_uart: add missing NULL check in h5_enqueue

    [ Upstream commit 32cb08e9 ]

    Syzbot hit general protection fault in __pm_runtime_resume(). The problem
    was in missing NULL check.

    hu->serdev can be NULL and we should not blindly pass &serdev->dev
    somewhere, since it will cause GPF.

Reported-by:  <syzbot+b9bd12fbed3485a3e51f@syzkaller.appspotmail.com>
    Fixes: d9dd833c ("Bluetooth: hci_h5: Add runtime suspend")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Signed-off-by: Mikhail Vanyulin <mikhail.vanyulin@rtsoft.de>