Enable system clock to the I2S module before accessing any I2S module registers:
- For system CPU run mode: PRCM:I2SCLKGR.CLK_EN = 1 (loaded with PRCM:CLKLOADCTL)
- For system CPU sleep mode: PRCM:I2SCLKGS.CLK_EN = 1 (loaded with PRCM:CLKLOADCTL)
- For system CPU deep-sleep mode: PRCM:I2SCLKGDS.CLK_EN = 1 (loaded with PRCM:CLKLOADCTL)