net: phylink: use neg_mode in phylink_mii_c22_pcs_decode_state()

Rather than using the state of the Autoneg bit, which is unreliable
with the new PCS neg mode support, use the passed neg_mode to decide
whether to decode the link partner advertisement data.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/E1tXGed-000EtF-CN@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Russell King (Oracle)

drivers/net/phy/phylink.c

@@ -3877,11 +3877,15 @@ void phylink_mii_c22_pcs_decode_state(struct phylink_link_state *state,
 {
 	state->link = !!(bmsr & BMSR_LSTATUS);
 	state->an_complete = !!(bmsr & BMSR_ANEGCOMPLETE);
-	/* If there is no link or autonegotiation is disabled, the LP advertisement
-	 * data is not meaningful, so don't go any further.
+
+	/* If the link is down, the advertisement data is undefined. */
+	if (!state->link)
+		return;
+
+	/* If in-band is disabled, then the advertisement data is not
+	 * meaningful.
 	 */
-	if (!state->link || !linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-					       state->advertising))
+	if (neg_mode != PHYLINK_PCS_NEG_INBAND_ENABLED)
 		return;
 
 	switch (state->interface) {