Fix the way the local advertising flow options are determined

Fix the way the local advertising flow options are determined

Local flow control options needed in order to resolve the negotiation
are incorrectly calculated.

Previously 'mii_advertise_flowctrl' was called to determine the local advertising
options, but these were determined based on FLOW_CTRL_RX/TX flags which are
never set through ethtool.
The patch simply translates from ethtool flow options to mii flow options.

Signed-off-by: Pavaluca Matei <matei.pavaluca@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>