net/mlx5: Move internal timer read function to clock library

Move mlx5_read_internal_timer() into lib/clock.c file as it is being
used there. As such, make this function a static one.

In addition, rearrange headers include to support function move.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Reviewed-by: Aya Levin <ayal@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>