Add inline attribute to `ch_get_idx` (AUD-5067)

[jesserockz]

When using v2.6 with a c++ project (ESPHome - ESP-IDF v4.4.5) I was getting this linking error.

Linking .pioenvs/s3-box-3-wakenet/firmware.elf
~/.platformio/packages/toolchain-xtensa-esp32s3@8.4.0+2021r2-patch5/bin/../lib/gcc/xtensa-esp32s3-elf/8.4.0/../../../../xtensa-esp32s3-elf/bin/ld: missing --end-group; added as last command line option
~/.platformio/packages/toolchain-xtensa-esp32s3@8.4.0+2021r2-patch5/bin/../lib/gcc/xtensa-esp32s3-elf/8.4.0/../../../../xtensa-esp32s3-elf/bin/ld: .pioenvs/s3-box-3-wakenet/esp-idf/audio_recorder/libaudio_recorder.a(recorder_sr.o):(.literal.feed_task+0x20): undefined reference to `ch_get_idx'
~/.platformio/packages/toolchain-xtensa-esp32s3@8.4.0+2021r2-patch5/bin/../lib/gcc/xtensa-esp32s3-elf/8.4.0/../../../../xtensa-esp32s3-elf/bin/ld: .pioenvs/s3-box-3-wakenet/esp-idf/audio_recorder/libaudio_recorder.a(recorder_sr.o): in function `ch_sort_16bit_4ch':
<project-folder>/components/audio_recorder/include/ch_sort.h:114: undefined reference to `ch_get_idx'
~/.platformio/packages/toolchain-xtensa-esp32s3@8.4.0+2021r2-patch5/bin/../lib/gcc/xtensa-esp32s3-elf/8.4.0/../../../../xtensa-esp32s3-elf/bin/ld: <project-folder>/components/audio_recorder/include/ch_sort.h:115: undefined reference to `ch_get_idx'
~/.platformio/packages/toolchain-xtensa-esp32s3@8.4.0+2021r2-patch5/bin/../lib/gcc/xtensa-esp32s3-elf/8.4.0/../../../../xtensa-esp32s3-elf/bin/ld: <project-folder>/components/audio_recorder/include/ch_sort.h:116: undefined reference to `ch_get_idx'
collect2: error: ld returned 1 exit status
*** [.pioenvs/s3-box-3-wakenet/firmware.elf] Error 1

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[jason-mao]

@jesserockz Thank you for your contributions. It's fixed on https://github.com/espressif/esp-adf/commit/f8190eac69c3f252a04b24fb525bdd64f46cb9ff

[jesserockz]

Thanks @jason-mao