arm64: dts: qcom: sc7280: Set the default dr_mode for usb2

Set the default dr_mode for usb2 node to "otg" to enable
role-switch for EUD(Embedded USB Debugger) connector node.

Signed-off-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/451392a942f90aa9805b00afad7dff894604d189.1649235218.git.quic_schowdhu@quicinc.com