cpufreq: blocklist Qualcomm sc8280xp and sa8540p in cpufreq-dt-platdev

The Qualcomm sc8280xp and sa8540p platforms also uses the
qcom-cpufreq-hw driver, so add them to 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>