phy devices: use same arg types

sparse complains about differing types from prototype to
definition, so change the u32 to phy_interface_t:

drivers/net/phy/phy_device.c:140:19: error: symbol 'phy_connect' redeclared with different type (originally declared at include/linux/phy.h:362) - incompatible argument 5 (different signedness)
drivers/net/phy/phy_device.c:190:19: error: symbol 'phy_attach' redeclared with different type (originally declared at include/linux/phy.h:360) - incompatible argument 4 (different signedness)

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>