cpufreq: dbx500: Move clk_get to probe

The armss clock shall only be fetched at probe thus move this here.
Same thing goes for the printing of the available frequencies.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>