Fix FUNC_GPIO0_CLK_OUT1 issue

[pera]

This PR puts FUNC_GPIO0_CLK_OUT1 (soc/esp32/register/soc/io_mux_reg.h) behind a flag: Without this change faust2esp32 output can only be compiled for ESP32 target chip (the name is confusing so just to be clear, this is not referring to the family but the original ESP32). For example, my target ESP32S3 doesn't compile because this define doesn't exist in soc/esp32s3/register/soc/io_mux_reg.h. Maybe this could be configurable but I don't believe it's strictly necessary.

Extracted from https://github.com/grame-cncm/faust/pull/1187