brcm47xx: b44: some fixes in combination with the switch

Let the switch start the carrier and set the duplex mode independently 
if this nic is up of not.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39733 3c298f89-4303-0410-b956-a3cf2f4a3e73