net: dsa: vsc73xx: pass value in phy_write operation

In the 'vsc73xx_phy_write' function, the register value is missing,
and the phy write operation always sends zeros.

This commit passes the value variable into the proper register.

Fixes: 05bd97fc ("net: dsa: Add Vitesse VSC73xx DSA router driver")
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/vitesse-vsc73xx-core.c

@@ -574,7 +574,7 @@ static int vsc73xx_phy_write(struct dsa_switch *ds, int phy, int regnum,
 		return 0;
 	}
 
-	cmd = (phy << 21) | (regnum << 16);
+	cmd = (phy << 21) | (regnum << 16) | val;
 	ret = vsc73xx_write(vsc, VSC73XX_BLOCK_MII, 0, 1, cmd);
 	if (ret)
 		return ret;