ext: stm32cube: update stm32l4xx cube version

Update Cube version for STM32L4XX family
from version: V1.10.0
to version: V1.12.0

This version solves patch in drivers/include/stm32l4xx_ll_spi.h

Note: git shows 100% diff on all files.
You need to tick "Ignore space change" in git UI to see real
differences. I tried different things to fix this without
success (dos2unix, file encoding, files access right).

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>