dt-bindings: i2c: spacemit: add support for K1 SoC

The I2C of K1 supports fast-speed-mode and high-speed-mode,
and supports FIFO transmission.

Signed-off-by: Troy Mitchell <troymitchell988@gmail.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20250319-k1-i2c-master-v8-1-013e2df2b78d@gmail.com