iwlwifi: provide gso_type to GSO packets

iwlwifi: provide gso_type to GSO packets

net/core/tso.c got recent support for USO, and this broke iwlfifi
because the driver implemented a limited form of GSO.

Providing ->gso_type allows for skb_is_gso_tcp() to provide
a correct result.

Fixes: 3d5b459ba0e3 ("net: tso: add UDP segmentation support")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Ben Greear <greearb@candelatech.com>
Tested-by: Ben Greear <greearb@candelatech.com>
Cc: Luca Coelho <luciano.coelho@intel.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209913
Link: https://lore.kernel.org/r/20210125150949.619309-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>