net/mlx5: Replace kfree with kvfree

Variable allocated by kvmalloc should not be freed by kfree.
Because it may be allocated by vmalloc.
So replace kfree with kvfree here.

Fixes: 9b1f2982 ("net/mlx5: Add support for FW fatal reporter dump")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>