Revert "USB: gadget: u_ether: Fix data stall issue in RNDIS tethering mode"

This reverts commit 78281f6e.

This data stall fix is no longer required in AOSP. It is already
skipped in android-4.9 patchset. Also core change from this
data stall fix is already undone by android-4.4 merge commit
324e88de ("Merge tag 'v4.4.32' into android-4.4.y").

This revert patch just clean up the left overs. It also reverts the
compile fix from Change-Id: I38c4f4a850b0329fb4a06b2c7e45558e16d66151
40ceb2c6 ("usb: gadget: Fix compilation problem with tx_qlen field").

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>