net/mlx5e: Fix UDP GSO for encapsulated packets

[ Upstream commit 83fea49f ]

When the skb is encapsulated, adjust the inner UDP header instead of the
outer one, and account for UDP header (instead of TCP) in the inline
header size calculation.

Fixes: 689adf0d ("net/mlx5e: Add UDP GSO support")
Reported-by: Jason Baron <jbaron@akamai.com>
Closes: https://lore.kernel.org/netdev/c42961cb-50b9-4a9a-bd43-87fe48d88d29@akamai.com/


Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Boris Pismenny <borisp@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>