Now works on Samsung Series 5 (chromebook)

Two fixes here:
o use 0x7F mask for phymode
o read phyid *AFTER* phy is powered up (via GPIOs)
Signed-off-by: Allan Chou <allan@asix.com.tw>
Signed-off-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>