sfc: Fix bugs in RX queue flushing

Avoid overrunning the hardware limit of 4 concurrent RX queue flushes.
Expand the queue flush state to support this.  Make similar changes to
TX flushing to keep the code symmetric.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2 files changed