ahci: imx: Explicitly clear IMX6Q_GPR13_SATA_MPLL_CLK_EN

We must clear this IMX6Q_GPR13_SATA_MPLL_CLK_EN bit on i.MX6Q, otherwise
Linux will fail to find the attached drive on some boards.

This entire fix was:
Reported-by: Eric Nelson <eric.nelson@boundarydevices.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Richard Zhu <r65037@freescale.com>
Cc: Linux-IDE <linux-ide@vger.kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org

drivers/ata/ahci_imx.c

@@ -113,7 +113,7 @@ static int imx6q_sata_init(struct device *dev, void __iomem *mmio)
 	/*
 	 * set PHY Paremeters, two steps to configure the GPR13,
 	 * one write for rest of parameters, mask of first write
-	 * is 0x07fffffd, and the other one write for setting
+	 * is 0x07ffffff, and the other one write for setting
 	 * the mpll_clk_en.
 	 */
 	regmap_update_bits(imxpriv->gpr, 0x34, IMX6Q_GPR13_SATA_RX_EQ_VAL_MASK
@@ -124,6 +124,7 @@ static int imx6q_sata_init(struct device *dev, void __iomem *mmio)
 			| IMX6Q_GPR13_SATA_TX_ATTEN_MASK
 			| IMX6Q_GPR13_SATA_TX_BOOST_MASK
 			| IMX6Q_GPR13_SATA_TX_LVL_MASK
+			| IMX6Q_GPR13_SATA_MPLL_CLK_EN
 			| IMX6Q_GPR13_SATA_TX_EDGE_RATE
 			, IMX6Q_GPR13_SATA_RX_EQ_VAL_3_0_DB
 			| IMX6Q_GPR13_SATA_RX_LOS_LVL_SATA2M