dt-bindings: connector: add typec-power-opmode property to usb-connector

Power operation mode may depends on hardware design, so, add the optional
property typec-power-opmode for usb-c connector to select the power
operation mode capability.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>