ARM: sun5i: Add clock indices

The A10s and A13 gates have a non continuous set of clock IDs that are
valid. Add the clock-indices property to the DT to express this.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>