dt-bindings: i2c: nxp,pnx-i2c: allow clocks property

Allow clocks property to fix below CHECK_DTB warnings:
arch/arm/boot/dts/nxp/lpc/lpc3250-ea3250.dtb: i2c@300 (nxp,pnx-i2c): Unevaluated properties are not allowed ('clocks' was unexpected)

Signed-off-by: Frank Li <[e-mail]>
Reviewed-by: Vladimir Zapolskiy <[e-mail]>
Signed-off-by: Andi Shyti <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/i2c/nxp,pnx-i2c.yaml

···
   interrupts:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
   clock-frequency:
     default: 100000