qlcnic: support rcv ring configuration through ethtool

o Support ethtool command ETHTOOL_GCHANNELS and ETHTOOL_SCHANNELS.
o Number of rcv rings configuration depend upon number of msix vector.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>