usb: dwc3: Add support for assignment of GSI EP interrupt number

Add support for the dynamic assignment of gsi endpoint interrupt
number, according to number of gsi hardware endpoints
supported by the hardware. The assignment of EP interrupt
number is removed from f_gsi.c file.

Change-Id: Idd7729e22c76c05cc826bb1d3fce2e4ce253307c
Signed-off-by: Aniket Randive <arandive@codeaurora.org>