dt-bindings: PCI: dwc: Detach common RP/EP DT bindings

dt-bindings: PCI: dwc: Detach common RP/EP DT bindings

Currently both DW PCIe Root Port and End-point DT bindings are defined as
separate schemas. Carefully looking at them, at the hardware reference
manuals and seeing there is a generic part of the driver used by the both
RP and EP drivers we can greatly simplify the DW PCIe controller bindings
by moving some of the properties into the common DT schema. It concerns
the PERST GPIO control, number of lanes, number of iATU windows and CDM
check properties. They will be defined in the snps,dw-pcie-common.yaml
schema which will be referenced in the DW PCIe Root Port and End-point DT
bindings in order to evaluate the common for both of these controllers
properties. The rest of properties like reg{,-names}, clock{s,-names},
reset{s,-names}, etc will be consolidate there in one of the next commits.

Link: https://lore.kernel.org/r/20221113191301.5526-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>