net: add phylink managed WoL and convert stmmac

Hi,

This experimental series is implementing the thoughts of Andrew,
Florian and myself in an attempt to improve the quality of Wake-on-Lan
(WoL) implementations.

This changes nothing for MAC drivers that do not wish to participate in
this, but if they do, then they gain the benefit of phylink configuring
WoL at the point closest to the media as possible.

We first need to solve the problem that the multitude of PHY drivers
report their device supports WoL, but are not capable of waking the
system. Correcting this is fundamental to choosing where WoL should be
enabled - a mis-reported WoL support can render WoL completely
ineffective.

The only PHY drivers which uses the driver model's wakeup support is
drivers/net/phy/broadcom.c, and until recently, realtek. This means
we have the opportunity for PHY drivers to be _correctly_ converted
to use this method of signalling wake-up capability only when they can
actually wake the system, and thus providing a way for phylink to
know whether to use PHY-based WoL at all.

However, a PHY driver not implementing that logic doesn't become a
blocker to MACs wanting to convert. In full, the logic is:

- phylink supports a flag, wol_phy_legacy, which forces phylink to use
  the PHY-based WoL even if the MDIO device is not marked as wake-up
  capable.

- when wol_phy_legacy is not set, we check whether the PHY MDIO device
  is wake-up capable. If it is, we offer the WoL request to the PHY.

- if neither wol_phy_legacy is set, or the PHY is not wake-up capable,
  we do not offer the WoL request to the PHY.

In both cases, after setting any PHY based WoL, we remove the options
that the PHY now reports are enabled from the options mask, and offer
these (if any) to the MAC. The mac will get a "mac_set_wol()" method
call when any settings change.

Phylink mainatains the WoL state for the MAC, so there's no need for
a "mac_get_wol()" method. There may be the need to set the initial
state but this is not supported at present.

I've also added support for doing the PHY speed-up/speed-down at
suspend/resume time depending on the WoL state, which takes another
issue from the MAC authors.

Lastly, with phylink now having the full picture for WoL, the
"mac_wol" argument for phylink_suspend() becomes redundant, and for
MAC drivers that implement mac_set_wol(), the value passed becomes
irrelevant.

 drivers/net/ethernet/stmicro/stmmac/stmmac.h       | 11 +--
 .../net/ethernet/stmicro/stmmac/stmmac_ethtool.c   | 31 +-------
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c  | 45 ++++++-----
 .../net/ethernet/stmicro/stmmac/stmmac_platform.c  |  4 +-
 drivers/net/phy/phy_device.c                       | 14 +++-
 drivers/net/phy/phylink.c                          | 89 +++++++++++++++++++++-
 include/linux/phy.h                                | 21 +++++
 include/linux/phylink.h                            | 28 +++++++
 8 files changed, 179 insertions(+), 64 deletions(-)

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