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

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 <wei.fang@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250829050615.1247468-3-wei.fang@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>