Merge branch 'switchdev-transaction-item-queue'

NETEVENT_NEIGH_UPDATE.  The device can be programmed with resolved nexthops

for the routes as arp_tbl updates.  The driver implements ndo_neigh_destroy

to know when arp_tbl neighbor entries are purged from the port.

Transaction item queue

^^^^^^^^^^^^^^^^^^^^^^

For switchdev ops attr_set and obj_add, there is a 2 phase transaction model

used. First phase is to "prepare" anything needed, including various checks,

memory allocation, etc. The goal is to handle the stuff that is not unlikely

to fail here. The second phase is to "commit" the actual changes.

Switchdev provides an inftrastructure for sharing items (for example memory

allocations) between the two phases.

The object created by a driver in "prepare" phase and it is queued up by:

switchdev_trans_item_enqueue()

During the "commit" phase, the driver gets the object by:

switchdev_trans_item_dequeue()

If a transaction is aborted during "prepare" phase, switchdev code will handle

cleanup of the queued-up objects.