PCI: qcom: Use PHY_REFCLK_USE_PAD only for ipq8064

The use of PHY_REFCLK_USE_PAD introduced a regression for apq8064 devices.
It was tested that while apq doesn't require the padding, ipq SoC must use
it or the kernel hangs on boot.

Link: https://lore.kernel.org/r/20201019165555.8269-1-ansuelsmth@gmail.com
Fixes: de3c4bf6 ("PCI: qcom: Add support for tx term offset for rev 2.1.0")
Reported-by: NIlia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: NIlia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: NAnsuel Smith <ansuelsmth@gmail.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NStanimir Varbanov <svarbanov@mm-sol.com>
Cc: stable@vger.kernel.org	# v4.19+

drivers/pci/controller/dwc/pcie-qcom.c

@@ -400,6 +400,8 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
 
 	/* enable external reference clock */
 	val = readl(pcie->parf + PCIE20_PARF_PHY_REFCLK);
+	/* USE_PAD is required only for ipq806x */
+	if (!of_device_is_compatible(node, "qcom,pcie-apq8064"))
 		val &= ~PHY_REFCLK_USE_PAD;
 	val |= PHY_REFCLK_SSP_EN;
 	writel(val, pcie->parf + PCIE20_PARF_PHY_REFCLK);