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

For dual speed gadget, with current no. of request(10), there is
possibility of corner case occurence where all 10 reuqests are queued
to HW without setting IOC bit, which could lead to data stall in
RNDIS tethering and RNDIS local networking.

With this patch, counter will be incremented before queueing request to
HW and sets IOC bit for every nth request due to which the corner case
of all requests queued to HW without IOC bit set will be avoided.

Change-Id: I26515bfd9bbc8f7af38be7835692143f7093118a
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>