Merge branch 'mv88e6xxx-counters'

Tobias Waldekranz says:

====================
net: dsa: mv88e6xxx: Add "eth-mac" and "rmon" counter group support

The majority of the changes (2/8) are about refactoring the existing
ethtool statistics support to make it possible to read individual
counters, rather than the whole set.

4/8 tries to collect all information about a stat in a single place
using a mapper macro, which is then used to generate the original list
of stats, along with a matching enum. checkpatch is less than amused
with this construct, but prior art exists (__BPF_FUNC_MAPPER in
include/uapi/linux/bpf.h, for example).

To support the histogram counters from the "rmon" group, we have to
change mv88e6xxx's configuration of them. Instead of counting rx and
tx, we restrict them to rx-only. 6/8 has the details.

With that in place, adding the actual counter groups is pretty
straight forward (5,7/8).

Tie it all together with a selftest (8/8).

v3 -> v4:
- Return size_t from mv88e6xxx_stats_get_stats
- Spelling errors in commit message of 6/8
- Improve selftest:
  - Report progress per-bucket
  - Test both ports in the pair
  - Increase MTU, if required

v2 -> v3:
- Added 6/8
- Added 8/8

v1 -> v2:
- Added 1/6
- Added 3/6
- Changed prototype of stats operation to reflect the fact that the
  number of read stats are returned, no errors
- Moved comma into MV88E6XXX_HW_STAT_MAPPER definition
- Avoid the construction of mapping table iteration which relied on
  struct layouts outside of mv88e6xxx's control
====================

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