gve: Enable hw-gro by default if device supported

gve: Enable hw-gro by default if device supported

Change the driver's default behavior to enable hw-gro whenever supported
for device.

Performance observations:
- We observed ~10% improvement in RX single stream throughput across
  various MTU sizes.
- No change in TCP_RR/TCP_CRR latencies

Signed-off-by: Ankit Garg <nktgrg@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
Link: https://patch.msgid.link/20260303195549.2679070-5-joshwash@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>