riscv: dts: add initial support for EIC7700 SoC

riscv: dts: add initial support for EIC7700 SoC

Add initial support for EIC7700 SoC that uses a SiFive Quad-Core
P550 CPU cluster.

This file is expected to grow as more device drivers are added to the
kernel.

Signed-off-by: Min Lin <linmin@eswincomputing.com>
Co-developed-by: Pritesh Patel <pritesh.patel@einfochips.com>
Signed-off-by: Pritesh Patel <pritesh.patel@einfochips.com>
Co-developed-by: Darshan Prajapati <darshan.prajapati@einfochips.com>
Signed-off-by: Darshan Prajapati <darshan.prajapati@einfochips.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Tested-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Pinkesh Vaghela <pinkesh.vaghela@einfochips.com>
Link: https://lore.kernel.org/r/20250825132427.1618089-6-pinkesh.vaghela@einfochips.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>