* I2C driver can have 2 backends:
* I2C_BACKEND_BUILTIN: Use (if present) the builtin i2c hardware.
* I2C_BACKEND_BITBANG: Use the emulated bitbang driver.
* I2C driver can have 2 backends:
* I2C_BACKEND_BUILTIN: Use (if present) the builtin i2c hardware.
* I2C_BACKEND_BITBANG: Use the emulated bitbang driver.