arm: mvebu: armada-xp/37x.dtsi: Sync PCIe DT nodes with Linux v4.20

arm: mvebu: armada-xp/37x.dtsi: Sync PCIe DT nodes with Linux v4.20

This patch sync's the PCIe DT nodes with the recent Linux v4.20 version.
This change makes it easier to reference specific PCIe nodes in the
board dts files to e.g. enable a PCIe port as this is now necessary with
the new DM PCI driver for these platforms.

Signed-off-by: Stefan Roese <[email protected]>
Cc: Dirk Eibach <[email protected]>
Cc: Mario Six <[email protected]>
Cc: Chris Packham <[email protected]>
Cc: Phil Sutter <[email protected]>
Cc: Marek Behún <[email protected]>
Cc: VlaoMao <[email protected]>
Cc: Tom Rini <[email protected]>