Input: sunkbd - avoid use-after-free in teardown paths

mainline inclusion
from mainline-v5.10-rc5
commit 77e70d35
category: bugfix
bugzilla: NA
CVE: CVE-2020-25669

--------------------------------

We need to make sure we cancel the reinit work before we tear down the
driver structures.

Reported-by: Bodong Zhao <nopitydays@gmail.com>
Tested-by: Bodong Zhao <nopitydays@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>