sky2: dont set bogus bit in PHY register

This code inherited from the sk98lin driver is incorrect on the Yukon2.
The GPHY_CTRL register values are specific to the internal PHY of the chip
and the values used were leftovers.
Driver was setting bit 13 which is now the INT polarity for the PHY!

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>