PCI: rockchip: Clean up bit definitions for PCIE_RC_CONFIG_LCS

PCIE_RC_CONFIG_LCS contains control and status bits specific to the PCIe
link.  The layout for this register looks the same as the existing
PCI_EXP_LNKCTL and PCI_EXP_LNKSTA.  So let's reuse them.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>