net: phy: micrel: use devm_clk_get_optional_enabled for the rmii-ref clock

While the external clock input will most likely be enabled, it's not
guaranteed and clk_get_rate in some suppliers will even just return
valid results when the clock is running.

So use devm_clk_get_optional_enabled to retrieve and enable the clock
in one go.
Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231201150131.326766-2-heiko@sntech.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/micrel.c

@@ -2001,7 +2001,7 @@ static int kszphy_probe(struct phy_device *phydev)
 
 	kszphy_parse_led_mode(phydev);
 
-	clk = devm_clk_get(&phydev->mdio.dev, "rmii-ref");
+	clk = devm_clk_get_optional_enabled(&phydev->mdio.dev, "rmii-ref");
 	/* NOTE: clk may be NULL if building without CONFIG_HAVE_CLK */
 	if (!IS_ERR_OR_NULL(clk)) {
 		unsigned long rate = clk_get_rate(clk);