ARM: ux500: Remove cpufreq platform device

The cpufreq device is already added from the prcmu driver as
a mfd child device.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>