phy: rockchip-pcie: Reconstruct driver to support per-lane PHYs

Reconstruct the whole driver to support per-lane PHYs.  Note that we could
also support the legacy PHY if you don't provide argument to
rockchip_pcie_phy_of_xlate().

Tested-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
[bhelgaas: use postincrement/decrement when order doesn't matter, uninline
to_pcie_phy() so decl fits on one line]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>