ARM: dts: ux500: snowball: Remove unused PRCMU cpufreq node

ARM: dts: ux500: snowball: Remove unused PRCMU cpufreq node

Commit a435adbec264 ("ARM: dts: augment Ux500 to use DT cpufreq")
switched the Ux500 device tree to use the generic DT cpufreq driver
and removed the PRCMU cpufreq node.

The snowball DTS still references it, without effect, since cpufreq
is now enabled by default. Remove the unused node.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20191117222732.283673-1-stephan@gerhold.net
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>