net/mlx5: fix VXLAN-GPE item translation

net/mlx5: fix VXLAN-GPE item translation

Currently, when using VXLAN-GPE or VXLAN item in the flow
both are being treated the same with flags 0x8 in VXLAN
header. Which mean the matching of the item VXLAN-GPE
will match any VXLAN packet.

This fixes the translation of VXLAN GPE item into PMD flow
item. Which will by default set the flags to VXLAN-GPE
to be 0xc.

Fixes: 3d69434113d1 ("net/mlx5: add Direct Verbs validation function")
Cc: stable@dpdk.org
Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>