ionic: use mutex to protect queue operations

The ionic_wait_on_bit_lock() was a open-coded mutex knock-off
used only for protecting the queue reset operations, and there
was no reason not to use the real thing.  We can use the lock
more correctly and to better protect the queue stop and start
operations from cross threading.  We can also remove a useless
and expensive bit operation from the Rx path.

This fixes a case found where the link_status_check from a link
flap could run into an MTU change and cause a crash.

Fixes: beead698

 ("ionic: Add the basic NDO callbacks for netdev support")
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>