dwc3: trace: Remove unused field with dwc3 request tracing

Commit 0bd0f6d2 ("usb: dwc3: gadget: remove allocated/queued request
tracking") removed  usage of allocated/queued request functionality but
didn't remove allocated/queued field which are now not used and being
initialized. Hence remove those unused fields.

Change-Id: I3ca6b94acddfe2bd790ea229e86c6d777f268538
Signed-off-by: Mayank Rana <mrana@codeaurora.org>