PCI: rockchip: Set Target Link Speed to 5.0 GT/s before retraining

Rockchip controllers can support up to 5.0 GT/s link speed. But the driver
doesn't set the Target Link Speed currently. This may cause failure in
retraining the link to 5.0 GT/s if supported by the endpoint. So set the
Target Link Speed to 5.0 GT/s in the Link Control and Status Register 2.

Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support")
Signed-off-by: Geraldo Nascimento <[e-mail]>
[mani: fixed whitespace warning, commit message rewording, added fixes tag]
Signed-off-by: Manivannan Sadhasivam <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>
Tested-by: Robin Murphy <[e-mail]>
Cc: [e-mail]
Link: https://patch.msgid.link/0afa6b[e-mail]

drivers/pci/controller/pcie-rockchip-host.c

···
 		 * Enable retrain for gen2. This should be configured only after
 		 * gen1 finished.
 		 */
+		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
+		status &= ~PCI_EXP_LNKCTL2_TLS;
+		status |= PCI_EXP_LNKCTL2_TLS_5_0GT;
+		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
 		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL);
 		status |= PCI_EXP_LNKCTL_RL;
 		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL);