doc: Add a new migration guide entry to USB

Rename the phy_handle property to phy-handle in
the devicetree and bindings of the USB subsystem.

Signed-off-by: James Roy <[email protected]>

Author: rruuaanng

doc/releases/migration-guide-4.1.rst

@@ -295,6 +295,11 @@ Timer
 * Renamed the ``compatible`` from ``nxp,kinetis-ftm`` to :dtcompatible:`nxp,ftm` and relocate it
   under ``dts/bindings/timer``.
 
+USB
+===
+
+* Renamed the devicetree property names ``phy_handle`` to ``phy-handle``.
+
 Video
 =====