docs: i2c: convert to ReST and add to driver-api bookset

Convert each file at I2C subsystem, renaming them to .rst and
adding to the driver-api book.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/hwmon/tmp103.rst

@@ -30,4 +30,4 @@ The driver provides the common sysfs-interface for temperatures (see
 Documentation/hwmon/sysfs-interface.rst under Temperatures).
 
 Please refer how to instantiate this driver:
-Documentation/i2c/instantiating-devices
+Documentation/i2c/instantiating-devices.rst