Add cmsis-core version variable

[cosmikwolf]

CMSIS core is locked to verison v5.6.0 in cmake/stm32/devices.cmake, but 5.9.0 has been released

There should be a variable that allows the user to set the CMSIS core version

[Hish15]

Hello @cosmikwolf, your idea makes sense, we could introduce

set(STM32_CMSIS_VERSION 5.9.0 CACHE STRING "Version of cmsis_core to fetch when using the stm32_fetch_cmsis function")

You can do one two things :

• Open a PR to change this one line

  stm32-cmake/cmake/stm32/devices.cmake

  Line 169 in 5f5c92c

  GIT_TAG v5.6.0

• Introduce the proposed variable, and document it, more lines, but better solution.

[ashen1queter]

Hey there, created a pr (#352 ) regarding the above.