dt-bindings: i2c: atmel,at91sam: correct path to i2c-controller schema

The referenced i2c-controller.yaml schema is provided by dtschema
package (outside of Linux kernel), so use full path to reference it.

Cc: [e-mail]
Fixes: 7ea75dd386be ("dt-bindings: i2c: convert i2c-at91 to json-schema")
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: Conor Dooley <[e-mail]>
Signed-off-by: Andi Shyti <[e-mail]>

Documentation/devicetree/bindings/i2c/atmel,at91sam-i2c.yaml

···
   - clocks
 
 allOf:
-  - $ref: i2c-controller.yaml
+  - $ref: /schemas/i2c/i2c-controller.yaml#
   - if:
       properties:
         compatible: