net/mlx5: switch Rx timestamp to dynamic mbuf field

net/mlx5: switch Rx timestamp to dynamic mbuf field

The mbuf timestamp is moved to a dynamic field
in order to allow removal of the deprecated static field.
The related mbuf flag is also replaced.

The dynamic offset and flag are stored in struct mlx5_rxq_data
to favor cache locality.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: David Christensen <drc@linux.vnet.ibm.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
Acked-by: David Marchand <david.marchand@redhat.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>