dt-bindings: cpufreq: cpufreq-qcom-hw: Add SM8550 compatible

Add compatible for EPSS CPUFREQ-HW on SM8550.
Also document the interrupts.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>