cpufreq: qcom: Don't add frequencies without an OPP

The driver currently adds all frequencies from the hardware LUT to
the cpufreq table, regardless of whether the corresponding OPP
exists. This prevents devices from disabling certain OPPs through
the device tree and can result in CPU frequencies for which the
interconnect bandwidth can't be adjusted. Only add frequencies
with an OPP entry.

Fixes: 55538fbc ("cpufreq: qcom: Read voltage LUT and populate OPP")
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>