cpufreq: scmi: Fix use-after-free in scmi_cpufreq_exit()

This issue was detected with the help of Coccinelle. So
change the order of function calls to fix it.

Fixes: 1690d8bb (cpufreq: scpi/scmi: Fix freeing of dynamic OPPs)

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: 4.20+ <stable@vger.kernel.org> # 4.20+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>