dt-bindings: PCI: ti,am65: Fix "ti,syscon-pcie-id"/"ti,syscon-pcie-mode" to take argument

Fix binding documentation of "ti,syscon-pcie-id" and "ti,syscon-pcie-mode"
to take phandle with argument. The argument is the register offset within
"syscon" used to configure PCIe controller. Similar change for j721e is
discussed in [1]

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

Link: https://lore.kernel.org/r/20211126083119.16570-2-kishon@ti.com


Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>