dt-bindings: net: move ptp-timer property to ethernet-controller.yaml

For some Ethernet controllers, the PTP timer function is not integrated.
Instead, the PTP timer is a separate device and provides PTP Hardware
Clock (PHC) to the Ethernet controller to use, such as NXP FMan MAC,
ENETC, etc. Therefore, a property is needed to indicate this hardware
relationship between the Ethernet controller and the PTP timer.

Since this use case is also very common, it is better to add a generic
property to ethernet-controller.yaml. According to the existing binding
docs, there are two good candidates, one is the "ptp-timer" defined in
fsl,fman-dtsec.yaml, and the other is the "ptimer-handle" defined in
fsl,fman.yaml. From the perspective of the name, the former is more
straightforward, so move the "ptp-timer" from fsl,fman-dtsec.yaml to
ethernet-controller.yaml.

Signed-off-by: Wei Fang <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Reviewed-by: Frank Li <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/devicetree/bindings/net/ethernet-controller.yaml

···
     $ref: "#/properties/phy-handle"
     deprecated: true
 
+  ptp-timer:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Specifies a reference to a node representing an IEEE 1588 PTP device.
+
   rx-fifo-depth:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:

Documentation/devicetree/bindings/net/fsl,fman-dtsec.yaml

···
       An array of two references: the first is the FMan RX port and the second
       is the TX port used by this MAC.
 
-  ptp-timer:
-    $ref: /schemas/types.yaml#/definitions/phandle
-    description: A reference to the IEEE1588 timer
-
   phys:
     description: A reference to the SerDes lane(s)
     maxItems: 1