spi: dt-bindings: mxs-spi: allow clocks properpty

Allow clocks property to fix below CHECK_DTB warnings:
arch/arm/boot/dts/nxp/mxs/imx28-btt3-0.dtb: spi@80014000 (fsl,imx28-spi): Unevaluated properties are not allowed ('clocks' was unexpected)

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20250528222821.728544-1-Frank.Li@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: nxpfrankli

Documentation/devicetree/bindings/spi/mxs-spi.yaml

@@ -24,6 +24,9 @@ properties:
   interrupts:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
   dmas:
     maxItems: 1