rockchip: rk3288: Revert MAC_TXCLK in pinctrl for GMAC

This reverts TXCLK toggling that was accidently dropped while reworking
commit 2454b719fb ("rockchip: rk3288: Add pinctrl support for the gmac
ethernet interface"). So the TX clock is enabled and we can use
GMAC_ROCKCHIP in 1Gbps when basic PINCTRL support is enabled
(!PINTRL_FULL).

Fixes: 2454b719fb ("rockchip: rk3288: Add pinctrl support for the...")
Signed-off-by: Romain Perier <romain.perier@collabora.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

drivers/pinctrl/rockchip/pinctrl_rk3288.c

@@ -496,6 +496,10 @@ static void pinctrl_rk3288_gmac_config(struct rk3288_grf *grf, int gmac_id)
 			     (GPIO_PULL_NORMAL << GPIO_PULL_SHIFT(6)) |
 			     (GPIO_PULL_NORMAL << GPIO_PULL_SHIFT(7)));
 
+		rk_clrsetreg(&grf->gpio4bl_iomux,
+			    GPIO4B1_MASK << GPIO4B1_SHIFT,
+			    GPIO4B1_MAC_TXCLK << GPIO4B1_SHIFT);
+
 		/* switch GPIO4B1 to 12ma drive-strength */
 		rk_clrsetreg(&grf->gpio1_e[3][1],
 			     GPIO_BIAS_MASK << GPIO_BIAS_SHIFT(1),