net: ar8216: sync mib_work cancellation

Import from https://chromium.googlesource.com/chromiumos/third_party/kernel/+/c05af20272059e149e2da2e1fa1fbd90c03ec979


Signed-off-by: Pavel Kubelun <be.dissent@gmail.com>

CHROMIUM: drivers: ar8216: sync mib_work cancellation

ar8xxx_mib_stop() is called from ar8xxx_phy_remove(), so we want to make
sure the work doesn't run after priv is freed / the device ceases to
exist.

BUG=chrome-os-partner:33096
TEST=none

Change-Id: Iafb44ce93a87433adc4576e5fea5fda58d1f43a9
Signed-off-by: Mathieu Olivari <mathieu@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/232827


Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Toshi Kikuchi <toshik@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Tested-by: Toshi Kikuchi <toshik@chromium.org>