mlxsw: spectrum: Fix the shift of FID field in TX header

Currently, the field FID in TX header is defined, but is not used as it is
relevant only for data packets. mlxsw driver currently sends all
host-generated traffic as control packets and not as data packets.

In Spectrum-2 and Spectrum-3, the correction field of PTP packets which
are sent as control packets is not updated at egress port. To overcome this
limitation while adding support for PTP, some packets will be sent as data
packets.

Fix the wrong shift in the definition, to allow using the field later.

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>