Revert "usb: dwc3: gadget: start requests as soon as they come"

This reverts commit 1d6a3918 ("usb:
dwc3: gadget: start requests as soon as they come"). Queuing request
as soon as they come without waiting for XFER_NOT_READY event resulting
into usb transfer stall.

Change-Id: Ic08b2da2983a520a07a0b225254c068d499a67cc
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>