Revert "geneve: pull IP header before ECN decapsulation"

This reverts commit 4179b00c ("geneve: pull IP header before ECN decapsulation").

Eric says: "network header should have been pulled already before
hitting geneve_rx()". Let's revert the syzbot fix since it's causing
more harm than good, and revisit.

Suggested-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: 4179b00c ("geneve: pull IP header before ECN decapsulation")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=210569
Link: https://lore.kernel.org/netdev/CANn89iJVWfb=2i7oU1=D55rOyQnBbbikf+Mc6XHMkY7YX-yGEw@mail.gmail.com/


Signed-off-by: Jakub Kicinski <kuba@kernel.org>