net/mlx4: fix spelling mistake: "Inrerface" -> "Interface" and rephrase message

Trivial fix to spelling mistake in mlx4_dbg debug message and also
change the phrasing of the message so that is is more readable

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>