usb: gadget: f_gsi: use accelerated EP for ECM IN with cv2x

Driver supports platforms that have three hardware accelerated
USB GSI endpoints.
RMNET cv2x always uses accelerated EPs, and if enabled with
RMNET LTE then HW accelerated EPs are used for cv2x and normal
EPs for LTE. And 3rd accelerated EP is used for ADPL.
If ECM is enabled with RMNET cv2x then configure HW accelerated
EP for ECM IN and normal EPs for ECM OUT and ADPL.

Change-Id: Ib9ac9f055e246005f096a249c54cc417e45d8538
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>