net/mlx5e: Allow dissector meta key in tc flower

Recently, fl_flow_key->indev_ifindex int field was refactored into
flow_dissector_key_meta field. With this, flower classifier also sets
FLOW_DISSECTOR_KEY_META flow dissector key. However, mlx5 flower dissector
validation code rejects filters that use flow dissector keys that are not
supported. Add FLOW_DISSECTOR_KEY_META to the list of allowed dissector
keys in __parse_cls_flower() to prevent following error when offloading
flower classifier to mlx5:

Error: mlx5_core: Unsupported key.

Fixes: 8212ed77 ("net: sched: cls_flower: use flow_dissector for ingress ifindex")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>