net/mlx5: Fix memory leak in cmd_exec()

If cmd_exec() is called with callback and mlx5_cmd_invoke() returns an
error, resources allocated in cmd_exec() will not be freed.

Fix the code to release the resources if mlx5_cmd_invoke() returns an
error.

Fixes: f0864701 ("net/mlx5: cmdif, Return value improvements")
Reported-by: Alex Tereshkin <atereshkin@nvidia.com>
Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Vlad Dumitrescu <vdumitrescu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1752753970-261832-2-git-send-email-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>