usb: phy: mxs: Add sync time after controller clear phcd

After clear portsc.phcd, PHY needs 200us stable time for switch
32K clock to AHB clock.

Signed-off-by: Peter Chen <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/phy/phy-mxs-usb.c

···
 	return mxs_phy->data == &imx6sl_phy_data;
 }
 
+/*
+ * PHY needs some 32K cycles to switch from 32K clock to
+ * bus (such as AHB/AXI, etc) clock.
+ */
+static void mxs_phy_clock_switch_delay(void)
+{
+	usleep_range(300, 400);
+}
+
 static int mxs_phy_hw_init(struct mxs_phy *mxs_phy)
 {
 	int ret;
···
 	int ret;
 	struct mxs_phy *mxs_phy = to_mxs_phy(phy);
 
+	mxs_phy_clock_switch_delay();
 	ret = clk_prepare_enable(mxs_phy->clk);
 	if (ret)
 		return ret;
···
 		       x->io_priv + HW_USBPHY_CTRL_SET);
 		clk_disable_unprepare(mxs_phy->clk);
 	} else {
+		mxs_phy_clock_switch_delay();
 		ret = clk_prepare_enable(mxs_phy->clk);
 		if (ret)
 			return ret;