phy: freescale: imx8m-pcie: assert phy reset during power on

After U-Boot initializes PCIe with "pcie enum", Linux fails to detect
an NVMe disk on some boot cycles with:

phy phy-32f00000.pcie-phy.0: phy poweron failed --> -110

Discussion with NXP identified that the iMX8MP PCIe PHY PLL may fail to
lock when re-initialized without a reset cycle [1].

The issue reproduces on 7% of tested hardware platforms, with a 30-40%
failure rate per affected device across boot cycles.

Insert a reset cycle in the power-on routine to ensure the PHY is
initialized from a known state.

[1] https://community.nxp.com/t5/i-MX-Processors/iMX8MP-PCIe-initialization-in-U-Boot/m-p/2248437#M242401

Signed-off-by: Rafael Beims <[e-mail]>
Cc: [e-mail]
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

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

···
 			writel(imx8_phy->tx_deemph_gen2,
 			       imx8_phy->base + PCIE_PHY_TRSV_REG6);
 		break;
-	case IMX8MP: /* Do nothing. */
+	case IMX8MP:
+		reset_control_assert(imx8_phy->reset);
 		break;
 	}