phy: freescale: imx8m-pcie: fix pcie link-up instability

Leaving AUX_PLL_REFCLK_SEL at its reset default of AUX_IN (PLL clock)
proves to be more stable on the i.MX 8M Mini.

Fixes: 1aa97b00 ("phy: freescale: pcie: Initialize the imx8 pcie standalone phy driver")
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
Link: https://lore.kernel.org/r/20240322130646.1016630-2-marcel@ziswiler.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/freescale/phy-fsl-imx8m-pcie.c

@@ -110,8 +110,10 @@ static int imx8_pcie_phy_power_on(struct phy *phy)
 		/* Source clock from SoC internal PLL */
 		writel(ANA_PLL_CLK_OUT_TO_EXT_IO_SEL,
 		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG062);
-		writel(AUX_PLL_REFCLK_SEL_SYS_PLL,
-		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG063);
+		if (imx8_phy->drvdata->variant != IMX8MM) {
+			writel(AUX_PLL_REFCLK_SEL_SYS_PLL,
+			       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG063);
+		}
 		val = ANA_AUX_RX_TX_SEL_TX | ANA_AUX_TX_TERM;
 		writel(val | ANA_AUX_RX_TERM_GND_EN,
 		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG064);