tools/power cpupower: Reset errno before strtoull()

cpuidle_state_get_one_value() never cleared errno before calling
strtoull(), so a prior ERANGE caused every cpuidle counter read to
return zero. Reset errno to 0 before the conversion so each sysfs read
is evaluated independently.

Link: https://lore.kernel.org/r/20251201121745.3776703-1-kaushlendra.kumar@intel.com
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: kaushlen

tools/power/cpupower/lib/cpuidle.c

@@ -150,6 +150,7 @@ unsigned long long cpuidle_state_get_one_value(unsigned int cpu,
 	if (len == 0)
 		return 0;
 
+	errno = 0;
 	value = strtoull(linebuf, &endp, 0);
 
 	if (endp == linebuf || errno == ERANGE)