blackfin-cpufreq: Change return type of cpu_set_cclk() to that of clk_set_rate()

The return type "unsigned long" was used by the cpu_set_cclk() function
while the type "int" is provided by the clk_set_rate() function.
Let us make this usage consistent.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/blackfin-cpufreq.c

@@ -112,7 +112,7 @@ static unsigned int bfin_getfreq_khz(unsigned int cpu)
 }
 
 #ifdef CONFIG_BF60x
-unsigned long cpu_set_cclk(int cpu, unsigned long new)
+int cpu_set_cclk(int cpu, unsigned long new)
 {
 	struct clk *clk;
 	int ret;