spi: spi-rockchip: add description for rv1126

The description below will be used for rv1126.dtsi or compatible one in
the future
Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Link: https://lore.kernel.org/r/20210621104800.19088-2-jon.lin@rock-chips.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/spi-rockchip.yaml

@@ -33,6 +33,7 @@ properties:
               - rockchip,rk3328-spi
               - rockchip,rk3368-spi
               - rockchip,rk3399-spi
+              - rockchip,rv1126-spi
           - const: rockchip,rk3066-spi
 
   reg: