i2c: i2c-stm32f7: Add initial SMBus protocols support

This patch adds SMBus support for I2C controller embedded in STM32F7 Soc.
All SMBus protocols are implemented except SMBus-specific protocols like
SMBus Host Notification and SMBus Alert protocols.

Implemented: SMBus Quick command, Send byte, Receive byte, Write byte/word,
read byte/word, Process call, Block write/read and Block write-block read
process call.

Signed-off-by: M'boumba Cedric Madianga <[email protected]>
Signed-off-by: Pierre-Yves MORDRET <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>

Author: stmordret