net: phylink: use pl->link_interface in phylink_expects_phy()

net: phylink: use pl->link_interface in phylink_expects_phy()

[ Upstream commit b63263555eaafbf9ab1a82f2020bbee872d83759 ]

The phylink_expects_phy() function allows MAC drivers to check if they are
expecting a PHY to attach. The checking condition in phylink_expects_phy()
aims to achieve the same result as the checking condition in
phylink_attach_phy().

However, the checking condition in phylink_expects_phy() uses
pl->link_config.interface, while phylink_attach_phy() uses
pl->link_interface.

Initially, both pl->link_interface and pl->link_config.interface are set
to SGMII, and pl->cfg_link_an_mode is set to MLO_AN_INBAND.

When the interface switches from SGMII to 2500BASE-X,
pl->link_config.interface is updated by phylink_major_config().
At this point, pl->cfg_link_an_mode remains MLO_AN_INBAND, and
pl->link_config.interface is set to 2500BASE-X.
Subsequently, when the STMMAC interface is taken down
administratively and brought back up, it is blocked by
phylink_expects_phy().

Since phylink_expects_phy() and phylink_attach_phy() aim to achieve the
same result, phylink_expects_phy() should check pl->link_interface,
which never changes, instead of pl->link_config.interface, which is
updated by phylink_major_config().

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Link: https://patch.msgid.link/20250227121522.1802832-2-yong.liang.choong@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>