net: phylink: add phylink managed MAC Wake-on-Lan support

net: phylink: add phylink managed MAC Wake-on-Lan support

Add core phylink managed Wake-on-Lan support, which is enabled when the
MAC driver fills in the new .mac_wol_set() method that this commit
creates.

When this feature is disabled, phylink acts as it has in the past,
merely passing the ethtool WoL calls to phylib whenever a PHY exists.
No other new functionality provided by this commit is enabled.

When this feature is enabled, a more inteligent approach is used.
Phylink will first pass WoL options to the PHY, read them back, and
attempt to set any options that were not set at the PHY at the MAC.

Since we have PHY drivers that report they support WoL, and accept WoL
configuration even though they aren't wired up to be capable of waking
the system, we need a way to differentiate between PHYs that think
they support WoL and those which actually do. As PHY drivers do not
make use of the driver model's wake-up infrastructure, but could, we
use this to determine whether PHY drivers can participate. This gives
a path forward where, as MAC drivers are converted to this, it
encourages PHY drivers to also be converted.

Phylink will also ignore the mac_wol argument to phylink_suspend() as
it now knows the WoL state at the MAC.

MAC drivers are expected to record/configure the Wake-on-Lan state in
their .mac_set_wol() method, and deal appropriately with it in their
suspend/resume methods. The driver model provides assistance to set the
IRQ wake support which may assist driver authors in achieving the
necessary configuration.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1vBrR2-0000000BLzU-1xYL@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>