clk: sunxi-ng: h6: Allow I2S to change parent rate

I2S doesn't work if parent rate couldn't be change. Difference between
wanted and actual rate is too big.

Fix this by adding CLK_SET_RATE_PARENT flag to I2S clocks.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>