net: stmmac: dwmac4: fix PCS duplex mode decode

dwmac4 was decoding the duplex mode from the GMAC_PHYIF_CONTROL_STATUS
register incorrectly, using GMAC_PHYIF_CTRLSTATUS_LNKMOD_MASK (value 1)
rather than GMAC_PHYIF_CTRLSTATUS_LNKMOD (bit 16). Fix this.

Fixes: 70523e6 ("drivers: net: stmmac: reworking the PCS code.")
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1sbJvd-001rGD-E3@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Russell King (Oracle)

drivers/net/ethernet/stmicro/stmmac/dwmac4.h

@@ -573,8 +573,6 @@ static inline u32 mtl_low_credx_base_addr(const struct dwmac4_addrs *addrs,
 #define GMAC_PHYIF_CTRLSTATUS_LNKSTS		BIT(19)
 #define GMAC_PHYIF_CTRLSTATUS_JABTO		BIT(20)
 #define GMAC_PHYIF_CTRLSTATUS_FALSECARDET	BIT(21)
-/* LNKMOD */
-#define GMAC_PHYIF_CTRLSTATUS_LNKMOD_MASK	0x1
 /* LNKSPEED */
 #define GMAC_PHYIF_CTRLSTATUS_SPEED_125		0x2
 #define GMAC_PHYIF_CTRLSTATUS_SPEED_25		0x1

drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c

@@ -786,7 +786,7 @@ static void dwmac4_phystatus(void __iomem *ioaddr, struct stmmac_extra_stats *x)
 		else
 			x->pcs_speed = SPEED_10;
 
-		x->pcs_duplex = (status & GMAC_PHYIF_CTRLSTATUS_LNKMOD_MASK);
+		x->pcs_duplex = (status & GMAC_PHYIF_CTRLSTATUS_LNKMOD);
 
 		pr_info("Link is Up - %d/%s\n", (int)x->pcs_speed,
 			x->pcs_duplex ? "Full" : "Half");