ARM: dts: augment Ux500 to use DT cpufreq

This adds the operating points to the Ux500 device tree and
deletes the old special-purpose cpufreq node, as we can now
use the generic DT cpufreq driver.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>