stm32l4: add clock control driver

Add the clock driver for the STM32L4 series.

Change-Id: Icdf79061f163d8d00187b382d1564422fb875c5b
Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
9 files changed