Merge branch 'dsa-b53-Turn-on-Broadcom-tags'

Florian Fainelli says:

====================
net: dsa: b53: Turn on Broadcom tags

This was long overdue, with this patch series, the b53 driver now
turns on Broadcom tags except for 5325 and 5365 which use an older
format that we do not support yet (TBD).

First patch is necessary in order for bgmac, used on BCM5301X and Northstar
Plus to work correctly and successfully send ARP packets back to the requsester.

Second patch is actually a bug fix, but because net/master and net-next/master
diverge in that area, I am targeting net-next/master here.

Finally, the last patch enables Broadcom tags after checking that the CPU port
selected is either, 5, 7 or 8, since those are the only valid combinations
given currently supported HW.

Changes in v3:

- guarded padding with netdev_uses_dsa() to let the non-DSA use cases
  not have a performance hit for smaller packets

- added missing select NET_DSA_TAG_BRCM to drivers/net/dsa/b53/Kconfig

Changes in v2:

- moved a hunk between patch 2 and patch 3 to avoid a bisectability issue
====================

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