net: mvneta: convert to phylink EEE implementation

net: mvneta: convert to phylink EEE implementation

Convert mvneta to use phylink's EEE implementation by implementing the
two LPI control methods, and adding the initial configuration and
capabilities.

Although disabling LPI requires clearing a single bit, for safety we
clear the manual mode and force bits to ensure that auto mode will be
used.

Enabling LPI needs a full configuration of several values, as the timer
values are dependent on the MAC operating speed, as per the original
code.

As Armada 388 states that EEE is only supported in "SGMII" modes, mark
this in lpi_interfaces. Testing with RGMII on the Clearfog platform
indicates that the receive path fails to detect LPI over RGMII.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/E1tYADv-0014Pt-NO@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>