i2c: add i2c driver for stm32

i2c: add i2c driver for stm32

Add i2c driver which can be used on both STM32F7 and STM32H7.
This I2C block supports the following features:
 _ Slave and master modes
 _ Multimaster capability
 _ Standard-mode (up to 100 kHz)
 _ Fast-mode (up to 400 kHz)
 _ Fast-mode Plus (up to 1 MHz)
 _ 7-bit and 10-bit addressing mode
 _ Multiple 7-bit slave addresses (2 addresses, 1 with configurable mask)
 _ All 7-bit addresses acknowledge mode
 _ General call
 _ Programmable setup and hold times
 _ Easy to use event management
 _ Optional clock stretching
 _ Software reset

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>