dt-bindings: clock: uniphier: Add clock binding for SoC-glue

Update binding document for clocks implemented in SoC-glue.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/1634000035-3114-5-git-send-email-hayashi.kunihiko@socionext.com
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/socionext,uniphier-clock.yaml

@@ -46,6 +46,9 @@ properties:
           - socionext,uniphier-ld20-peri-clock
           - socionext,uniphier-pxs3-peri-clock
           - socionext,uniphier-nx1-peri-clock
+      - description: SoC-glue clock
+        enum:
+          - socionext,uniphier-pro4-sg-clock
 
   "#clock-cells":
     const: 1