Add napi support

Before this patch

 iperf -s -i 1
 ------------------------------------------------------------
 Server listening on TCP port 5001
 TCP window size: 85.3 KByte (default)
 ------------------------------------------------------------
 [  4] local 10.192.242.153 port 5001 connected with 10.192.242.138 port 50004
 [ ID] Interval       Transfer     Bandwidth
 [  4]  0.0- 1.0 sec  41.2 MBytes   345 Mbits/sec
 [  4]  1.0- 2.0 sec  43.7 MBytes   367 Mbits/sec
 [  4]  2.0- 3.0 sec  42.8 MBytes   359 Mbits/sec
 [  4]  3.0- 4.0 sec  43.7 MBytes   367 Mbits/sec
 [  4]  4.0- 5.0 sec  42.7 MBytes   359 Mbits/sec
 [  4]  5.0- 6.0 sec  43.8 MBytes   367 Mbits/sec
 [  4]  6.0- 7.0 sec  43.0 MBytes   361 Mbits/sec

After this patch
 [  4]  2.0- 3.0 sec  51.6 MBytes   433 Mbits/sec
 [  4]  3.0- 4.0 sec  51.8 MBytes   435 Mbits/sec
 [  4]  4.0- 5.0 sec  52.2 MBytes   438 Mbits/sec
 [  4]  5.0- 6.0 sec  52.1 MBytes   437 Mbits/sec
 [  4]  6.0- 7.0 sec  52.1 MBytes   437 Mbits/sec
 [  4]  7.0- 8.0 sec  52.3 MBytes   439 Mbits/sec
Signed-off-by: Frank Li <Frank.Li@freescale.com>
Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>