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 <[email protected]>
Acked-by: Wolfram Sang <[email protected]>
Acked-by: Alexandre Belloni <[email protected]>
Acked-by: Jonathan Cameron <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
86 files changed