dt-bindings: clock: Add a missing include to MMP Audio Clock binding

The include file for input clock in the example was missing, breaking the
validation.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reported-by: Rob Herring <robh+dt@kernel.org>
Link: https://lore.kernel.org/r/20200605065258.567858-1-lkundrak@v3.sk
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/marvell,mmp2-audio-clock.yaml

@@ -59,6 +59,7 @@ additionalProperties: false
 examples:
   - |
     #include <dt-bindings/clock/marvell,mmp2-audio.h>
+    #include <dt-bindings/clock/marvell,mmp2.h>
     #include <dt-bindings/power/marvell,mmp2.h>
 
     clock-controller@d42a0c30 {