UPSTREAM: staging: gdm72xx: cancel work when driver unloads

UPSTREAM: staging: gdm72xx: cancel work when driver unloads

cancel the work function at driver unload stage and remove
the function from the queue

Cc: Ben Chan <benchan@chromium.org>
Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit c0352cb71d3d573a33af92d320f29f1c79d71b8b)

Change-Id: I8c4e522270b4acad07d125398b1afe4a14810f16
Signed-off-by: Ben Chan <benchan@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/49427
Reviewed-by: Paul Stewart <pstew@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>