ARM: sun5i: Add audio PLL

The A13 uses the PLL2 as the audio PLL, which is the parent of all the
other audio clocks in the system (i2s, codec, etc.). However, it has a
different divider configuration than the A10, hence the difference
compatible.

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