PCI: keystone: Use phandle argument from "ti,syscon-pcie-id"/"ti,syscon-pcie-mode"

PCI: keystone: Use phandle argument from "ti,syscon-pcie-id"/"ti,syscon-pcie-mode"

Get "syscon" pcie_mode and pcie_id offset from the argument of
"ti,syscon-pcie-id" and "ti,syscon-pcie-mode" phandle respectively.
Previously a subnode to "syscon" node was added which has the
exact memory mapped address of pcie_mode and pcie_id but now the
offset of pcie_mode and pcie_id within "syscon" is now being passed
as argument to "ti,syscon-pcie-id" and "ti,syscon-pcie-mode" phandle.

If the offset is not provided in "ti,syscon-pcie-id"/"ti,syscon-pcie-mode",
the full memory mapped address of pcie_ctrl is used in order to maintain
old DT compatibility.

Similar change for J721E is as discussed in [1]

[1] -> http://lore.kernel.org/r/CAL_JsqKiUcO76bo1GoepWM1TusJWoty_BRy2hFSgtEVMqtrvvQ@mail.gmail.com

Link: https://lore.kernel.org/r/20211126083119.16570-3-kishon@ti.com
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>