clk: mvebu: staticize of_cpu_clk_setup

This symbol is used only in this file. The patch fix the following
sparse warning:
warning: symbol 'of_cpu_clk_setup' was not declared. Should it be static?
Signed-off-by: NJisheng Zhang <jszhang@marvell.com>
Acked-by: NJason Cooper <jason@lakedaemon.net>
Acked-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

drivers/clk/mvebu/clk-cpu.c

@@ -101,7 +101,7 @@ static const struct clk_ops cpu_ops = {
 	.set_rate = clk_cpu_set_rate,
 };
 
-void __init of_cpu_clk_setup(struct device_node *node)
+static void __init of_cpu_clk_setup(struct device_node *node)
 {
 	struct cpu_clk *cpuclk;
 	void __iomem *clock_complex_base = of_iomap(node, 0);