hal: stm32l0x: Add HAL for the STM32L0x series

This adds the HAL code needed for the SoC in a later patch for
the stm32l0 series.

Origin: ST Microelectronics
License: BSD-3-Clause
URL: http://www.st.com/en/embedded-software/stm32cubel0.html


Commit: 1.10.0
Purpose: HAL layer for stm32l0
Maintained-by: External

Signed-off-by: Endre Karlson <endre.karlson@gmail.com>