clk: at91: sam9x60: fix usb clock parents

SAM9X60's USB clock has 3 parents: plla, upll and main_osc.

Fixes: 01e2113d ("clk: at91: add sam9x60 pmc driver")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lkml.kernel.org/r/1579261009-4573-3-git-send-email-claudiu.beznea@microchip.comAcked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/at91/sam9x60.c

@@ -234,9 +234,8 @@ static void __init sam9x60_pmc_setup(struct device_node *np)
 
 	parent_names[0] = "pllack";
 	parent_names[1] = "upllck";
-	parent_names[2] = "mainck";
-	parent_names[3] = "mainck";
-	hw = sam9x60_clk_register_usb(regmap, "usbck", parent_names, 4);
+	parent_names[2] = "main_osc";
+	hw = sam9x60_clk_register_usb(regmap, "usbck", parent_names, 3);
 	if (IS_ERR(hw))
 		goto err_free;