PCI: rockchip: Use local struct device pointer consistently

We have a local "struct device *dev" in rockchip_pcie_probe().  Use it
consistently throughout the function.  No functional change intended.

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