riscv: dts: eswin: add HiFive Premier P550 board device tree

Add minimal device tree for HiFive Premier P550 Development board

Currently the data populated in this DT file is for UART.

Signed-off-by: Min Lin <linmin@eswincomputing.com>
Co-developed-by: Pinkesh Vaghela <pinkesh.vaghela@einfochips.com>
Signed-off-by: Pinkesh Vaghela <pinkesh.vaghela@einfochips.com>
Tested-by: Samuel Holland <samuel.holland@sifive.com>
Tested-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20250825132427.1618089-7-pinkesh.vaghela@einfochips.com


Signed-off-by: Arnd Bergmann <arnd@arndb.de>