cpufreq: speedstep-lib: Use int type to store negative error codes

cpufreq: speedstep-lib: Use int type to store negative error codes

Change the return type of the speedstep_get_freqs() function from unsigned
int to int because it may return negative error codes.  For the same
reason, change the 'ret' variables to int type as well.

No effect on runtime.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20250902114545.651661-4-rongqianfeng@vivo.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>