asix: Don't reset PHY on if_up for ASIX 88772

I've noticed every time the interface is set to 'up,', the kernel
reports that the link speed is set to 100 Mbps/Full Duplex, even
when ethtool is used to set autonegotiation to 'off', half
duplex, 10 Mbps.
It can be tested by:
 ifconfig eth0 down
 ethtool -s eth0 autoneg off speed 10 duplex half
 ifconfig eth0 up

Then checking 'dmesg' for the link speed.

Signed-off-by: Michel Stam <m.stam@fugro.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>