dt-bindings: clocks: add rk3288w variant compatible

Add the possible compatible "rockchip,rk3288w-cru" that handles
the difference between the rk3288 and the new revision rk3288w.

This compatible will be added by bootloaders.
Signed-off-by: Mylène Josserand <mylene.josserand@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200602080644.11333-3-mylene.josserand@collabora.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/clock/rockchip,rk3288-cru.txt

@@ -4,9 +4,15 @@ The RK3288 clock controller generates and supplies clock to various
 controllers within the SoC and also implements a reset controller for SoC
 peripherals.
 
+A revision of this SoC is available: rk3288w. The clock tree is a bit
+different so another dt-compatible is available. Noticed that it is only
+setting the difference but there is no automatic revision detection. This
+should be performed by bootloaders.
+
 Required Properties:
 
-- compatible: should be "rockchip,rk3288-cru"
+- compatible: should be "rockchip,rk3288-cru" or "rockchip,rk3288w-cru" in
+  case of this revision of Rockchip rk3288.
 - reg: physical base address of the controller and length of memory mapped
   region.
 - #clock-cells: should be 1.