clk: sunxi-ng: h6: Use sigma-delta modulation for audio PLL

Audio devices needs exact clock rates in order to correctly reproduce
the sound. Until now, only integer factors were used to configure H6
audio PLL which resulted in inexact rates. Fix that by adding support
for fractional factors using sigma-delta modulation look-up table. It
contains values for two most commonly used audio base frequencies.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <mripard@kernel.org>