usb: gadget: f_gsi: Use SW path for ECM if RMNET_V2X is bound

When both ECM and V2X instances are enabled in a composition, use
hardware accelerated EPs for V2X instance and normal EPs for ECM.
In general, set channel parameter flag 'is_sw_path' to true for
channels using normal USB EPs.

Change-Id: I855bbf1e87be65e0fa53c78a49422ac7eab3ca1b
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>