include/linux/phy/phy.h: fix minor kerneldoc errors

Correct two minor kerneldoc errors:

 1) missing reference to @mode in struct phy_ops
 2) obsolete reference to @init_data in struct_phy_attrs,
    removed in dbc98635

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>