dt-bindings: vendor-prefixes: add Siflower

Shanghai Siflower Communication Co. is a manufacturer for home router SoCs.
Add a vendor prefix for it.

Link: http://www.siflower.com.cn/en


Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20241223034350.215375-1-gch981213@gmail.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>