arm: sunxi: Add clock definitions for the new clock driver

This introduces proper clock definitions on sunxi.dtsi, to be used
with the new clock driver for sunxi.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>