ARM: imx6q: register phy fixup only when CONFIG_PHYLIB is enabled

It fixes the following compile error with network disabled in
imx_v6_v7_defconfig.

arch/arm/mach-imx/built-in.o: In function `ksz9021rn_phy_fixup':
imx53-dt.c:(.text+0x5f70): undefined reference to `mdiobus_write'
imx53-dt.c:(.text+0x5f84): undefined reference to `mdiobus_write'
imx53-dt.c:(.text+0x5f98): undefined reference to `mdiobus_write'
imx53-dt.c:(.text+0x5fac): undefined reference to `mdiobus_write'
imx53-dt.c:(.text+0x5fc0): undefined reference to `mdiobus_write'
arch/arm/mach-imx/built-in.o: In function `imx6q_init_machine':
imx53-dt.c:(.init.text+0x387c): undefined reference to `phy_register_fixup_for_uid'
make: *** [.tmp_vmlinux1] Error 1
Reported-by: Artem Bityutskiy <dedekind1@gmail.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/mach-imx6q.c

@@ -63,6 +63,7 @@ void imx6q_restart(char mode, const char *cmd)
 /* For imx6q sabrelite board: set KSZ9021RN RGMII pad skew */
 static int ksz9021rn_phy_fixup(struct phy_device *phydev)
 {
+	if (IS_ENABLED(CONFIG_PHYLIB)) {
 		/* min rx data delay */
 		phy_write(phydev, 0x0b, 0x8105);
 		phy_write(phydev, 0x0c, 0x0000);
@@ -71,12 +72,14 @@ static int ksz9021rn_phy_fixup(struct phy_device *phydev)
 		phy_write(phydev, 0x0b, 0x8104);
 		phy_write(phydev, 0x0c, 0xf0f0);
 		phy_write(phydev, 0x0b, 0x104);
+	}
 
 	return 0;
 }
 
 static void __init imx6q_sabrelite_init(void)
 {
+	if (IS_ENABLED(CONFIG_PHYLIB))
 		phy_register_fixup_for_uid(PHY_ID_KSZ9021, MICREL_PHY_ID_MASK,
 				ksz9021rn_phy_fixup);
 }