cpufreq: qcom-hw: Add missing null pointer check

of_device_get_match_data() may return NULL, so add a check to prevent
potential null pointer dereference.

Issue reported by Qualcomm's internal static analysis tool.

Fixes: 4f796170

 ("cpufreq: qcom-hw: Move soc_data to struct qcom_cpufreq")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>