net/mlx5: Display the command index in command mailbox dump

Multiple commands can be printed at the same time which can
lead to wrong order of their lines in dmesg output.
As a result, it's hard to match data dumps to the correct command
or which command was fully dumped at some point.

Fix this by displaying the corresponding command index, and also
indicate when a command was fully dumped.

Signed-off-by: Alaa Hleihel <alaa@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>