cxgb4: fix Txq restart check during backpressure

cxgb4: fix Txq restart check during backpressure

[ Upstream commit f1f20a8666c55cb534b8f3fc1130eebf01a06155 ]

Driver reclaims descriptors in much smaller batches, even if hardware
indicates more to reclaim, during backpressure. So, fix the check to
restart the Txq during backpressure, by looking at how many
descriptors hardware had indicated to reclaim, and not on how many
descriptors that driver had actually reclaimed. Once the Txq is
restarted, driver will reclaim even more descriptors when Tx path
is entered again.

Fixes: d429005fdf2c ("cxgb4/cxgb4vf: Add support for SGE doorbell queue timer")
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>