net/mlx5: DR, Check device state when polling CQ

Calling fast teardown as part of the normal unloading caused
a problem with SW steering - SW steering still needs to clear
its tables, write to ICM and poll for completions.
When teardown has been done, SW steering keeps polling the CQ
forever, because nobody flushes it.

This patch fixes the issue by checking the device state in
cases where no CQE was returned.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>