Revert "usb: dwc3: gadget: track number of TRBs per request"

This reverts commit 2a2b1c4d.

This is a preparation change for merging android-4.19.57 into
msm-4.19 branch.

Reverted due to BootTimeRunner regression.

Change-Id: Ib84d83615c8b6de5443353d68ee804a6b035ca76
Signed-off-by: Ivaylo Georgiev <irgeorgiev@codeaurora.org>