net/mlx5: Fix error message when failing to allocate device memory

Fix spacing for the error and also the correct error code pointer.

Fixes: c9b9dcb4

 ("net/mlx5: Move device memory management to mlx5_core")
Signed-off-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>