spi/rockchip: add rk3036/rk3228/rk3368 SoCs for spi document

We had supported the rk3036/rk3066/rk3188/rk3228/rk3288/rk3368/rk3399
family SoCs in linux kernel.

Let's add the other SoCs, in order to a better understanding from the
rockchip spi document.

Signed-off-by: Caesar Wang <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

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

···
 Required Properties:
 
 - compatible: should be one of the following.
-    "rockchip,rk3066-spi" for rk3066.
-    "rockchip,rk3188-spi", "rockchip,rk3066-spi" for rk3188.
-    "rockchip,rk3288-spi", "rockchip,rk3066-spi" for rk3288.
-    "rockchip,rk3399-spi", "rockchip,rk3066-spi" for rk3399.
+    "rockchip,rk3036-spi" for rk3036 SoCS.
+    "rockchip,rk3066-spi" for rk3066 SoCs.
+    "rockchip,rk3188-spi" for rk3188 SoCs.
+    "rockchip,rk3228-spi" for rk3228 SoCS.
+    "rockchip,rk3288-spi" for rk3288 SoCs.
+    "rockchip,rk3368-spi" for rk3368 SoCs.
+    "rockchip,rk3399-spi" for rk3399 SoCs.
 - reg: physical base address of the controller and length of memory mapped
        region.
 - interrupts: The interrupt number to the cpu. The interrupt specifier format