net: stmmac: sunxi: convert to set_clk_tx_rate()

Convert sunxi to use the set_clk_tx_rate() callback rather than the
fix_mac_speed() callback.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1u4frU-000nMf-6o@rmk-PC.armlinux.org.uk


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