Revert "udp_tunnel: GRO optimizations"

Revert "udp_tunnel: GRO optimizations"

Revert "udp_tunnel: use static call for GRO hooks when possible"
This reverts commit 311b36574ceaccfa3f91b74054a09cd4bb877702.

Revert "udp_tunnel: create a fastpath GRO lookup."
This reverts commit 8d4880db378350f8ed8969feea13bdc164564fc1.

There are multiple small issues with the series. In the interest
of unblocking the merge window let's opt for a revert.

Link: https://lore.kernel.org/cover.1742557254.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>