clk: sun5i: Add compatibles for Allwinner A13

The A13 has a lot less clocks than the one found in the Allwinner A10.
Add these stripped down clocks to the clock driver and in the
documentation.

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