net/mlx5: Fix a bug of using ptp channel index as pin index

On PTP mlx5_ptp_enable(on=0) flow, driver mistakenly used channel index
as pin index.

After ptp patch marked in fixes tag was introduced, driver can freely
call ptp_find_pin() as part of the .enable() callback.

Fix driver mlx5_ptp_enable(on=0) flow to always use ptp_find_pin(). With
that, Driver will use the correct pin index in mlx5_ptp_enable(on=0) flow.

In addition, when initializing the pins, always set channel to zero. As
all pins can be attached to all channels, let ptp_set_pinfunc() to move
them between the channels.

For stable branches, this fix to be applied only on kernels that includes
both patches in fixes tag. Otherwise, mlx5_ptp_enable(on=0) will be stuck
on pincfg_mux.

Fixes: 62582a7e ("ptp: Avoid deadlocks in the programmable pin code.")
Fixes: ee7f1220

 ("net/mlx5e: Implement 1PPS support")
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Reviewed-by: Ariel Levkovich <lariel@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>