clk: imx: imx8mn: fix audio pll setting

The AUDIO PLL max support 650M, so the original clk settings violate
spec. This patch makes the output 786432000 -> 393216000,
and 722534400 -> 361267200 to aligned with NXP vendor kernel without any
impact on audio functionality and go within 650MHz PLL limit.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>