Merge branch 'Ethernet-Cable-test-support'

Merge branch 'Ethernet-Cable-test-support'

Andrew Lunn says:

====================
Ethernet Cable test support

any copper Ethernet PHY have support for performing diagnostics of
the cable. Are the cable shorted, broken, not plugged into anything at
the other end? And they can report roughly how far along the cable any
fault is.

Add infrastructure in ethtool and phylib support for triggering a
cable test and reporting the results. The Marvell 1G PHY driver is
then extended to make use of this infrastructure.

For testing, a modified ethtool(1) can be found here:
https://github.com/lunn/ethtool.git feature/cable-test-v4. This also
contains extra code for TDR dump, which will be added to the kernel in
a later patch series.

Thanks to Chris Healy for extensive testing.

v2:
See individual patches but:

Remove _REPLY messages
Change length into a u32
Grammar fixes
Rename functions for consistency
Extack for cable test already running
Remove ethnl_cable_test_act_ops
Add status attributes
Rename pairs from numbers to letters

v3:

See individual patches but:
Remove ETHTOOL_MSG_CABLE_TEST_ACT_REPLY from documentation
Remove unused cable_test_get_policy
Fixed example in document
Add ETHTOOL_A_CABLE_NEST_* enum
Add ETHTOOL_MSG_CABLE_TEST_NTF to documentation
Poison phydev->skb
Return -EMSGSIZE when ethnl_bcastmsg_put() fails
Return valid error code when nla_nest_start() fails
Use u8 for results
Actually put u32 length into message
s/mavell/marvell/g
Remove include of <uapi/linux/ethtool_netlink.h>
EMSGSIZE when ethnl_bcastmsg_put() fails
Print an error message on failure, since this is a void function.

v4:
See individual patches but:
Remove unwanted blank line
ENOTSUPP->EOPNOTSUPP
Move EINVAL->EMSGSIZE fix to correct patch
====================

Signed-off-by: Jakub Kicinski <kuba@kernel.org>