dt-bindings: cpufreq: cpufreq-qcom-hw: document interrupts

The Qualcomm Soc cpufreq hardware engine has LMh/thermal throttling
interrupts (already present in SM8250 and SM8450 DTS) and Linux driver
uses them:

  sm8250-hdk.dtb: cpufreq@18591000: 'interrupt-names', 'interrupts' do not match any of the regexes: 'pinctrl-[0-9]+'
  sm8450-qrd.dtb: cpufreq@17d91000: 'interrupt-names', 'interrupts' do not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>