thermal/drivers/cpufreq_cooling: Fix return of cpufreq_set_cur_state

When setting the cooling device current state from userspace via sysfs,
the operation fails by returning an -EINVAL.

It appears the recent changes with the per-policy frequency QoS
introduced a regression as reported by:

 https://lkml.org/lkml/2020/3/20/599



The function freq_qos_update_request returns 0 or 1 describing update
effectiveness, and a negative error code on failure. However,
cpufreq_set_cur_state returns 0 on success or an error code otherwise.

Consider the QoS update as successful if the function does not return
an error.

Fixes: 3000ce3c ("cpufreq: Use per-policy frequency QoS")
Signed-off-by: Willy Wolff <willy.mh.wolff.ml@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200321092740.7vvwfxsebcrznydh@macmini.local