ARM: dts: pxa: add pxa25x cpu operating points

Add the relevant data taken from the PXA 25x Electrical, Mechanical, and
Thermal Specfication. This will be input data for cpufreq-dt driver.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>