[CPUFREQ] db8500: support all frequencies

This adds support for the 200 MHz frequency mode of the
DB8500 SoC, and prints the available frequencies at init
time.

Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dave Jones <davej@redhat.com>