arm64: dts: mediatek: mt7988: Add devicetree for BananaPi R4 Pro

arm64: dts: mediatek: mt7988: Add devicetree for BananaPi R4 Pro

Add devicetree for Bpi-R4-Pro.

BananaPi R4 Pro is a MT7988A based board which exists in 2 different
hardware versions:

- 4E: 4 GB RAM and using internal 2.5G Phy for WAN-Combo
- 8X: 8 GB RAM and 2x Aeonsemi AS21010P 10G phys

common parts:

- MediaTek MT7988A Quad-core Arm Corex-A73,1.8GHz processor
- 8GB eMMC flash
- 256MB SPI-NAND Flash
- Micro SD card slot
- 1x 10G SFP+ WAN
- 1x 10G SFP+ LAN
- 4x 2.5G RJ45 LAN (MxL86252C)
- 1x 1G RJ45 LAN (MT7988 internal switch)
- 2x miniPCIe slots with PCIe3.0 2lane interface for Wi-Fi NIC
- 2x M.2 M-KEY slots with PCIe3.0 1lane interface for NVME SSD
- 3x M.2 B-KEY slots with USB3.2 for 5G Module (PCIe shared with key-m)
- 1x USB3.2 slot
- 1x USB2.0 slot
- 1x USB TypeC Debug Console
- 2x13 PIN Header for expanding application

https://docs.banana-pi.org/en/BPI-R4_Pro/BananaPi_BPI-R4_Pro

The PCIe is per default in key-m state and can be changed to key-b with
the pcie-overlays.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>