net/mlx5e: Rely on filter_dev instead of dissector keys for tunnels

Currently, tunnel attributes are parsed and inner header matching is used
only when flow dissector specifies match on some of the supported
encapsulation fields. When user tries to offload tc filter that doesn't
match any encapsulation fields on tunnel device, mlx5 tc layer incorrectly
sets to match packet header keys on encap header (outer header) and
firmware rejects the rule with syndrome 0x7e1579 when creating new flow
group.

Change __parse_cls_flower() to determine whether tunnel is used based on
fitler_dev tunnel info, instead of determining it indirectly by checking
flow dissector enc keys.

Fixes: bbd00f7e

 ("net/mlx5e: Add TC tunnel release action for SRIOV offloads")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>