It was missing and it wasn't possible to enable I2C (0 and/or 1)
before this fix.
To sum up, this fix implements a I2C register function in ESP32
bring-up routines (esp32_bringup.c) and call if for I2C0 and/or
I2C1 during ESP32 bringup (these function callings are conditioned
by CONFIG_ESP32_I2C (to check if I2C support has been configured),
CONFIG_ESP32_I2C0 (to check if I2C0 support has been configured)
and CONFIG_ESP32_I2C1 (to check if I2C1 support has been configured).
Once this fix is implemented, /dev/i2c0 and/or /dev/i2c1 interfaces
become available and work fine.
