dt-bindings: usb: hx3: Remove unneeded dr_mode

It is expected that the USB controller works in host mode
to have the USB hub operational.

Remove such unneeded property from the devicetree example.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Link: https://lore.kernel.org/r/20240405195051.945474-1-festevam@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>