dt-bindings: reset: Add parent "resets" property as optional

LD11 mio reset controller has a reset lines from system controller.
Add parent "resets" property to fix the following warning.

uniphier-ld11-global.dt.yaml: reset: 'resets' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: Documentation/devicetree/bindings/reset/socionext,uniphier-reset.yaml

Signed-off-by: Kunihiko Hayashi <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Philipp Zabel <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
   "#reset-cells":
     const: 1
 
+  resets:
+    maxItems: 1
+
 additionalProperties: false
 
 required: