net: stmmac: qcom-ethqos: use rgmii_clock() to set the link clock

The link clock operates at twice the RGMII clock rate. Therefore, we
can use the rgmii_clock() helper to set this clock rate.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1tlRMK-004Vsx-Ss@rmk-PC.armlinux.org.uk


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