opp: Fix adding OPP entries in a wrong order if rate is unavailable

Fix adding OPP entries in a wrong (opposite) order if OPP rate is
unavailable. The OPP comparison was erroneously skipped, thus OPPs
were left unsorted.

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Tested-by: Matt Merhar <mattmerhar@protonmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>