Merge branch 'mdb-get'

Ido Schimmel says:

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Add MDB get support

This patchset adds MDB get support, allowing user space to request a
single MDB entry to be retrieved instead of dumping the entire MDB.
Support is added in both the bridge and VXLAN drivers.

Patches #1-#6 are small preparations in both drivers.

Patches #7-#8 add the required uAPI attributes for the new functionality
and the MDB get net device operation (NDO), respectively.

Patches #9-#10 implement the MDB get NDO in both drivers.

Patch #11 registers a handler for RTM_GETMDB messages in rtnetlink core.
The handler derives the net device from the ifindex specified in the
ancillary header and invokes its MDB get NDO.

Patches #12-#13 add selftests by converting tests that use MDB dump with
grep to the new MDB get functionality.

iproute2 changes can be found here [1].

v2:
* Patch #7: Add a comment to describe attributes structure.
* Patch #9: Add a comment above spin_lock_bh().

[1] https://github.com/idosch/iproute2/tree/submit/mdb_get_v1
====================

Signed-off-by: David S. Miller <davem@davemloft.net>