tg3: Fix UDP fragments treated as RMCP

The 5762 devices sometimes incorrectly treat udp fragments as RMCP
packets and route to the APE. This patch sets the RX_MODE_IPV4_FRAG_FIX
bit for these devices which enables the proper behaviour.

Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>