dt-bindings: arm: cpus: Allow fsl,soc-operating-points for i.MX6

The old i.MX6 (over 10 years) chip use fsl,soc-operating-points to get
SoC's voltage and frequency information when cpu change frequency.

Set fsl,soc-operating-points deprecated.

Allow soc-supply property and set it deprecated.

Fix bunch of CHECK_DTBS warnings:
  arch/arm/boot/dts/nxp/imx/imx6ul-prti6g.dtb: cpu@0 (arm,cortex-a7): Unevaluated properties are not allowed ('fsl,soc-operating-points', 'soc-supply' were unexpected)
	from schema $id: http://devicetree.org/schemas/arm/cpus.yaml#

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250827210912.92029-1-Frank.Li@nxp.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/arm/cpus.yaml

@@ -347,10 +347,23 @@ properties:
     deprecated: true
     description: Use 'cpu-supply' instead
 
+  soc-supply:
+    deprecated: true
+    description: Only for i.MX6/7 Soc.
+
   sram-supply:
     deprecated: true
     description: Use 'mem-supply' instead
 
+  fsl,soc-operating-points:
+    $ref: /schemas/types.yaml#/definitions/uint32-matrix
+    description: FSL i.MX6 Soc operation-points when change cpu frequency
+    deprecated: true
+    items:
+      items:
+        - description: Frequency in kHz
+        - description: Voltage for OPP in uV
+
   mediatek,cci:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: Link to Mediatek Cache Coherent Interconnect