net: phy: microchip: Use genphy_soft_reset() to purge stale LPA bits

net: phy: microchip: Use genphy_soft_reset() to purge stale LPA bits

Enable .soft_reset for the LAN88xx PHY driver by assigning
genphy_soft_reset() to ensure that the phylib core performs a proper
soft reset during reconfiguration.

Previously, the driver left .soft_reset unimplemented, so calls to
phy_init_hw() (e.g., from lan88xx_link_change_notify()) did not fully
reset the PHY. As a result, stale contents in the Link Partner Ability
(LPA) register could persist, causing the PHY to incorrectly report
that the link partner advertised autonegotiation even when it did not.

Using genphy_soft_reset() guarantees a clean reset of the PHY and
corrects the false autoneg reporting in these scenarios.

Fixes: ccb989e4d1ef ("net: phy: microchip: Reset LAN88xx PHY to ensure clean link state on LAN7800/7850")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250709130753.3994461-2-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>