compat: backport ethtool_rxfh_indir_default()

compat: backport ethtool_rxfh_indir_default()

This was added via commit 278bc429:

mcgrof@frijol ~/linux-next (git::master)$ git describe --contains 278bc429
v3.3-rc1~182^2~191

commit 278bc4296bd64ffd1d3913b487dc8a520e423a7a
Author: Ben Hutchings <bhutchings@solarflare.com>
Date:   Thu Dec 15 13:56:49 2011 +0000

    ethtool: Define and apply a default policy for RX flow hash indirection

    All drivers that support modification of the RX flow hash indirection
    table initialise it in the same way: RX rings are assigned to table
    entries in rotation.  Make that default policy explicit by having them
    call a ethtool_rxfh_indir_default() function.

    In the ethtool core, add support for a zero size value for
    ETHTOOL_SRXFHINDIR, which resets the table to this default.

    Partly-suggested-by: Matt Carlson <mcarlson@broadcom.com>
    Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
    Acked-by: Shreyas N Bhatewara <sbhatewara@vmware.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>