net: stmmac: rk: remove need for ->set_speed() method

net: stmmac: rk: remove need for ->set_speed() method

As we can detect whether the SoC provides the parameters necessary for
rk_set_reg_speed(), we don't need to have explicit calls to this.
Instead, we can move the contents of this function to
rk_set_clk_tx_rate().

This remsoves all the .set_speed() implementations that merely go on to
invoke rk_set_reg_speed().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1vmqnM-00000007VD8-1xWo@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>