arm64: dts: imx8mp-msc-sm2s: Add sound card

The MSC SM2-MB-EP1 carrier board for the SM2S-IMX8PLUS SMARC module has an
NXP SGTL5000 audio codec connected to I2S-0 (sai2).

This requires to:

 * add the power supplies (always on)
 * enable sai2 with pinmuxes
 * reparent the CLKOUT1 clock that feeds the codec SYS_MCLK to
   IMX8MP_CLK_24M in order it to generate an accurate 24 MHz rate

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>