net/mlx4_en: Fixed crash when port type is changed

[ Upstream commit 1ec4864b10171b0691ee196d7006ae56d2c153f2 ]

timecounter_init() was was called only after first potential
timecounter_read().
Moved mlx4_en_init_timestamp() before mlx4_en_init_netdev()

Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>