I2S: more consistent usage of variables, really use apll rx setting

[Staars]

Description:

Besides some cosmetic refactoring, this should solve undefined behaviour with the I2S configuration for a microphone in standard mode. Needs more testing.

Increase default value for DMA frame number, which should now exactly match the minimal requirements for MP3 encoding with 16 bit at 32000 Hz.

Use apll setting in standard mode now.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.6
• The code change is tested and works with Tasmota core ESP32 V.3.0.0
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[sfromis]

When building with I2S Audio for ESP32-S3, I'm having a compile error hitting a line which was updated by this PR.

/tasmota/tasmota/tasmota_xdrv_driver/xdrv_42_0_i2s_3_lib_idf51.ino: In member function 'bool TasmotaI2S::startI2SChannel(bool, bool)':
xtensa-esp32s3-elf-g++ -o .pio/build/tasmota32s3/libaa8/Update/HttpsOTAUpdate.cpp.o .....
/tasmota/tasmota/tasmota_xdrv_driver/xdrv_42_0_i2s_3_lib_idf51.ino:673:44: error: 'I2S_CLK_SRC_APLL' was not declared in this scope; did you mean 'I2S_CLK_SRC_XTAL'?
  673 |               rx_std_cfg.clk_cfg.clk_src = I2S_CLK_SRC_APLL;
      |                                            ^~~~~~~~~~~~~~~~
      |                                            I2S_CLK_SRC_XTAL

(Truncated the very long command line)

My expectation was that I should not need to be looking at additional build options, or could there be something there?

[Staars]

Clearly my fault.
Thanks for reporting.
I pushed a PR.

[sfromis]

Thanks, with #21483 I'm seeing no more failed builds.