mac802154: rename dev_workqueue to workqueue

Small rename to use the name workqueue than dev_workqueue. To bring the
same naming convention like wireless into 802.15.4.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --cc net/mac802154/ieee802154_i.h
Simple merge

diff --cc net/mac802154/main.c
Simple merge

diff --cc net/mac802154/mib.c
Simple merge

diff --cc net/mac802154/rx.c
Simple merge

diff --cc net/mac802154/tx.c
Simple merge