interupt_controller/stm32_exti: driver for STM32 EXTI controller

Introcuce a driver for External Interrupt/Event Controller (EXTI) found
on STM32 MCUs.

Change-Id: Ib206521fcc51b5dfaaf5dea9d436f8304f3a36be
Origin: Original
Signed-off-by: Maciej Borzecki <maciek.borzecki@gmail.com>
6 files changed