PCI: imx6: Assert i.MX8MM CLKREQ# even if no device present

[ Upstream commit 45514f7 ]

The CLKREQ# signal is an open drain, active low signal that is driven
low by the remote Endpoint device. But it might not be driven low if no
Endpoint device is connected.

On i.MX8MM PCIe, phy_init() may fail and system boot may hang if no
Endpoint is connected to assert CLKREQ#.

Handle this as on i.MX8MQ, where we explicitly assert CLKREQ# so the
PHY can be initialized.

Link: https://lore.kernel.org/r/1645672013-8949-1-git-send-email-hongxing.zhu@nxp.com
Fixes: 178e244 ("PCI: imx: Add the imx8mm pcie support")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/pci/controller/dwc/pci-imx6.c

@@ -453,10 +453,6 @@ static int imx6_pcie_enable_ref_clk(struct imx6_pcie *imx6_pcie)
 	case IMX7D:
 		break;
 	case IMX8MM:
-		ret = clk_prepare_enable(imx6_pcie->pcie_aux);
-		if (ret)
-			dev_err(dev, "unable to enable pcie_aux clock\n");
-		break;
 	case IMX8MQ:
 		ret = clk_prepare_enable(imx6_pcie->pcie_aux);
 		if (ret) {