arm64: dts: imx8mq-librem5: add usb-role-switch property to dwc3

In order to enable (PD and data) role switching on the Librem 5 phone,
add the usb-role-switch property to imx8mq's dwc3 node.

Signed-off-by: Angus Ainslie <angus@akkea.ca>
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>