net/tap: fix zeroed flow mask configurations

net/tap: fix zeroed flow mask configurations

The rte_flow meaning of zero flow mask configuration is to match all
the range of the item value.
For example, the flow eth / ipv4 dst spec 1.2.3.4 dst mask 0.0.0.0
should much all the ipv4 traffic from the rte_flow API perspective.

>From some kernel perspectives the above rule means to ignore all the
ipv4 traffic (e.g. Ubuntu 16.04, 4.15.10).

Due to the fact that the tap PMD should provide the rte_flow meaning,
it is necessary to ignore the spec in case the mask is zero when it
forwards such like flows to the kernel.
So, the above rule should be translated to eth / ipv4 to get the
correct meaning.

Ignore spec configurations when the mask is zero.

Fixes: de96fe68ae95 ("net/tap: add basic flow API patterns and actions")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>