net: stmmac: rk: combine .set_*_speed() methods

As a result of the previous patches, many of the .set_rgmii_speed()
and .set_rmii_speed() implementations are identical apart from the
interface mode. Add a new .set_speed() function which takes the
interface mode in addition to the speed, and use it to combine the
separate implementations, calling the common rk_set_reg_speed()
function.

Also convert rk_set_clk_mac_speed() to be called by this new method
pointer, rather than having these implementations called from both
.set_*_speed() methods.

Remove all the error messages from the .set_speed() methods, as these
return an error code which is propagated up to stmmac_mac_link_up()
which will print the error.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1uPk39-004CFf-7a@rmk-PC.armlinux.org.uk


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