Revert "net/mlx5: Add retry mechanism to the command entry index allocation"

This reverts commit 410bd754.

The reverted commit had added a retry mechanism to the command entry
index allocation. The previous patch ensures that there is a free
command entry index once the command work handler holds the command
semaphore. Thus the retry mechanism is not needed.

Fixes: 410bd754 ("net/mlx5: Add retry mechanism to the command entry index allocation")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Eran Ben Elisha <eranbe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>