usb: dwc3: Add support for GSI event buffer configuration

Add additional event buffers for GSI based hardware accelerated
endpoints and its related configuration. This change moves USB
GSI endpoint related event buffer handling to glue driver from
DWC3 core driver.

CRs-Fixed: 1003784
Change-Id: Ibedf73690040b8bd872f5621835680a66c22e265
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>