cpufreq: SPEAr: clk_round_rate() can return a zero upon error

Treat both negative and zero return values from clk_round_rate()
as errors.  This is needed since subsequent patches will convert
clk_round_rate()'s return value to be an unsigned type, rather
than a signed type, since some clock sources can generate rates
higher than (2^31)-1 Hz.

Eventually, when calling clk_round_rate(), only a return value of
zero will be considered a error.  All other values will be
considered valid rates.  The comparison against values less than
0 is kept to preserve the correct behavior in the meantime.
Signed-off-by: NPaul Walmsley <pwalmsley@nvidia.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/spear-cpufreq.c

@@ -138,7 +138,7 @@ static int spear_cpufreq_target(struct cpufreq_policy *policy,
 	}
 
 	newfreq = clk_round_rate(srcclk, newfreq * mult);
-	if (newfreq < 0) {
+	if (newfreq <= 0) {
 		pr_err("clk_round_rate failed for cpu src clock\n");
 		return newfreq;
 	}