Merge branch 'lan78xx-minor-fixes'

Dave Stevenson says:

====================
lan78xx minor fixes

This is a small set of patches for the Microchip LAN78xx chip,
as used in the Raspberry Pi 3B+.
The main debug/discussion was on
https://github.com/raspberrypi/linux/issues/2458

Initial symptoms were that VLANs were very unreliable.
A couple of things were found:
- firstly that the hardware timeout value set failed to
  take into account the VLAN tag, so a full MTU packet
  would be timed out.
- second was that regular checksum failures were being
  reported. Disabling checksum offload confirmed that
  the checksums were valid, and further experimentation
  identified that it was only if the VLAN tags were being
  passed through to the kernel that there were issues.
  The hardware supports VLAN filtering and tag stripping,
  therefore those have been implemented (much of the work
  was already done), and the driver drops back to s/w
  checksums should the choice be made not to use the h/w
  VLAN stripping.
====================

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