net: wangxun: add flow control support

Add support to set pause params with ethtool -A and get pause
params with ethtool -a, for ethernet driver txgbe and ngbe.

Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>