net: ethtool support to configure number of channels

Ethtool support to configure RX, TX and other channels. combined field
in struct ethtool_channels to reflect set of channel (RX, TX or other).
Other channel can be link interrupts, SR-IOV coordination etc.

ETHTOOL_GCHANNELS will report max and current number of RX channels,
max and current number of TX channels, max and current number of other channel
or max and current number of combined channel.

Number of channel can be modify upto max number of channel through
ETHTOOL_SCHANNELS command.

Ben Hutchings:
o define 'combined' and 'other' types.  Most multiqueue drivers pair up RX and TX
  queues so that most channels combine RX and TX work.
o Please could you use a kernel-doc comment to describe the structure.

Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>