cpufreq: blacklist Qualcomm sc8180x in cpufreq-dt-platdev

The Qualcomm SC8180x platform uses the qcom-cpufreq-hw driver, so
it in the cpufreq-dt-platdev driver's blocklist.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>