net: gianfar: simplify init_phy()

Use phy_set_max_speed() to simplify init_phy().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/b863dcf7-31e8-45a1-a284-7075da958ff0@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>