dts: Add stm32 quadspi support on L4 series

Add device tree description for qspi node on STM32L4 and
signals on whole family.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>
2 files changed