dt-bindings: vendor-prefixes: add eswin

dt-bindings: vendor-prefixes: add eswin

Add new vendor string to dt bindings.
This new vendor string is used by
- ESWIN EIC770X SoC
- HiFive Premier P550 board which uses EIC7700 SoC.

Link: https://www.eswin.com/en/
Signed-off-by: Pritesh Patel <pritesh.patel@einfochips.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Pinkesh Vaghela <pinkesh.vaghela@einfochips.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250616112316.3833343-4-pinkesh.vaghela@einfochips.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>