bnxt: fix a condition

This code generates as static checker warning because htons(ETH_P_IPV6)
is always true.  From the context it looks like the && was intended to
be !=.

Fixes: 94758f8d

 ('bnxt_en: Add GRO logic for BCM5731X chips.')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>