ethernet: avoid retpoline overhead on TEB (GENEVE, NvGRE, VxLAN) GRO

The two most popular headers going after Ethernet are IPv4 and IPv6.
Retpoline overhead for them is addressed only in dev_gro_receive(),
when they lie right after the outermost Ethernet header.
Use the indirect call wrappers in TEB (Transparent Ethernet Bridging,
such as GENEVE, NvGRE, VxLAN etc.) GRO receive code to reduce the
penalty when processing the inner headers.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: David S. Miller <davem@davemloft.net>