I2C driver docs (#4298)

I2C driver docs (#4298)

* I2C driver docs

- Added I2C driver docs.
- Changed arm master i2c driver to have a weak i2c_init as it is impossible to account for all possible port configuration in the STM32 world.

* Update docs/i2c_driver.md

Co-Authored-By: yiancar <yiangosyiangou@cytanet.com.cy>
* Update docs/i2c_driver.md

Co-Authored-By: yiancar <yiangosyiangou@cytanet.com.cy>
* Update docs/i2c_driver.md

Co-Authored-By: yiancar <yiangosyiangou@cytanet.com.cy>
* Update docs/i2c_driver.md

Co-Authored-By: yiancar <yiangosyiangou@cytanet.com.cy>
* GPIO release fix