compat: define NETIF_F_RXCSUM

compat: define NETIF_F_RXCSUM

We can't really backport this so just define it.

mcgrof@frijol ~/linux-next (git::master)$ git describe --contains e83d360d
v2.6.39-rc1~468^2~336

commit e83d360d9a7e5d71d55c13e96b19109a2ea23bf0
Author: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Date:   Tue Feb 15 16:59:18 2011 +0000

    net: introduce NETIF_F_RXCSUM

    Introduce NETIF_F_RXCSUM to replace device-private flags for RX checksum
    offload. Integrate it with ndo_fix_features.

    ethtool_op_get_rx_csum() is removed altogether as nothing in-tree uses it.

    Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
    Signed-off-by: David S. Miller <davem@davemloft.net>
mcgrof@drvbp1 ~/compat (git::master)$ time ckmake

Trying kernel 3.6.5-030605-generic [OK]
Trying kernel 3.5.7-030507-generic [OK]
Trying kernel 3.4.17-030417-generic [OK]
Trying kernel 3.3.8-030308-generic [OK]
Trying kernel 3.2.33-030233-generic [OK]
Trying kernel 3.1.10-030110-generic [OK]
Trying kernel 3.0.50-030050-generic [OK]
Trying kernel 2.6.39-02063904-generic [OK]
Trying kernel 2.6.38-02063808-generic [OK]
Trying kernel 2.6.37-02063706-generic [OK]
Trying kernel 2.6.36-02063604-generic [OK]
Trying kernel 2.6.35-02063513-generic [OK]
Trying kernel 2.6.34-02063413-generic [OK]
Trying kernel 2.6.33-02063320-generic [OK]
Trying kernel 2.6.32-02063260-generic [OK]
Trying kernel 2.6.31-02063113-generic [OK]
Trying kernel 2.6.30-02063010-generic [OK]
Trying kernel 2.6.29-02062906-generic [OK]
Trying kernel 2.6.28-02062810-generic [OK]
Trying kernel 2.6.27-020627-generic [OK]
Trying kernel 2.6.26-020626-generic [OK]
Trying kernel 2.6.25-020625-generic [OK]
Trying kernel 2.6.24-020624-generic [OK]

real    1m59.783s
user    8m11.111s
sys     1m56.675s

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>