drivers: Add Atmel SAM family I2C (TWIHS) driver

Added I2C bus (TWIHS) driver for Atmel SAM MCU family. Only
I2C Master Mode with 7 bit addressing is currently supported.

Tested on Atmel SMART SAM E70 Xplained board

Origin: Original

Jira: ZEP-1866
Change-Id: Ic5aa7b6b21295feccae883d580b38bbeaf2ce291
Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>