bnxt_en: Don't treat single segment rx frames as GRO frames.

If hardware completes single segment rx frames, don't bother setting
up all the GRO related fields.  Pass the SKB up as a normal frame.

Reviewed-by: vasundhara volam <vvolam@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>