usb: dwc3-msm: Add GSI mode support for Normal USB EPs

Allow non-GSI capable or normal USB endpoint to be used
in GSI mode. In this case, USB driver receives events from
hardware and updates GSI doorbell register with completed
TRB. USB GSI hardware wrapper isn't involved for such EPs.
In order to use this feature, GSI function driver must
choose interrupter number as '0' with such endpoints,
non-zero interrupters are reserved for USB GSI wrapper use.

Change-Id: Ief51b722bbe1aa97ff806e5a3b8b1ca806671a8f
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>