ARM: sunxi: Register cpufreq-dt for sun[45678]i

On sun[45678]i, we have one cluster of identical cores sharing a
clock, which is ideal for using cpufreq-dt. Register a platform
device for cpufreq-dt.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>