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

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>