net: lan743x: convert to phylink managed EEE

Convert lan743x to phylink managed EEE:
- Set the lpi_capabilties.
- Move the call to lan743x_mac_eee_enable() into the enable/disable
  tx_lpi functions.
- Ensure that EEEEN is clear during probe.
- Move the setting of the LPI timer into mac_enable_tx_lpi().
- Move reading of LPI timer to phylink initialisation to set the
  default timer value.

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/E1tYAEB-0014QB-4s@rmk-PC.armlinux.org.uk


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