riscv: dts: microchip: add sevkit device tree

Add a basic dts for the Microchip Smart Embedded Vision dev kit.
The SEV kit is an upcoming first party board, featuring an MPFS250T and:
- Dual Sony Camera Sensors (IMX334)
- IEEE 802.11 b/g/n 20MHz (1x1) Wi-Fi
- Bluetooth 5 Low Energy
- 4 GB DDR4 x64
- 2 GB LPDDR4 x32
- 1 GB SPI Flash
- 8 GB eMMC flash & SD card slot (multiplexed)
- HDMI2.0 Video Input/Output
- MIPI DSI Output
- MIPI CSI-2 Input

Link: https://onlinedocs.microchip.com/pr/GUID-404D3738-DC76-46BA-8683-6A77E837C2DD-en-US-1/index.html?GUID-065AEBEE-7B2C-4895-8579-B1D73D797F06


Signed-off-by: Vattipalli Praveen <praveen.kumar@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>