clk: vt8500: Fix division-by-0 when requested rate=0

A request to vt8500_dclk_(round_rate/set_rate) with rate=0 results
in a division-by-0 in the kernel.
Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk-vt8500.c

@@ -121,7 +121,12 @@ static long vt8500_dclk_round_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long *prate)
 {
 	struct clk_device *cdev = to_clk_device(hw);
-	u32 divisor = *prate / rate;
+	u32 divisor;
+
+	if (rate == 0)
+		return 0;
+
+	divisor = *prate / rate;
 
 	/* If prate / rate would be decimal, incr the divisor */
 	if (rate * divisor < *prate)
@@ -142,9 +147,14 @@ static int vt8500_dclk_set_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long parent_rate)
 {
 	struct clk_device *cdev = to_clk_device(hw);
-	u32 divisor = parent_rate / rate;
+	u32 divisor;
 	unsigned long flags = 0;
 
+	if (rate == 0)
+		return 0;
+
+	divisor =  parent_rate / rate;
+
 	/* If prate / rate would be decimal, incr the divisor */
 	if (rate * divisor < *prate)
 		divisor++;