ARM: pxa: add clk_set_rate()

Since there're mulitple clock rates in some device controllers, enable
clk_set_rate() for this usage.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>
diff --git a/arch/arm/mach-mmp/clock.c b/arch/arm/mach-mmp/clock.c
index 886e056..7c6f95f 100644
--- a/arch/arm/mach-mmp/clock.c
+++ b/arch/arm/mach-mmp/clock.c
@@ -88,3 +88,18 @@
 	return rate;
 }
 EXPORT_SYMBOL(clk_get_rate);
+
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	unsigned long flags;
+	int ret = -EINVAL;
+
+	if (clk->ops->setrate) {
+		spin_lock_irqsave(&clocks_lock, flags);
+		ret = clk->ops->setrate(clk, rate);
+		spin_unlock_irqrestore(&clocks_lock, flags);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(clk_set_rate);