Added file to know the current versions of STM32 device CMSIS version

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

system/Drivers/CMSIS/Device/ST/STM32YYxx_CMSIS_version.md

@@ -0,0 +1,17 @@
+# STM32YYxx CMSIS version:
+
+  * STM32F0: 2.3.2
+  * STM32F1: 4.1.0
+  * STM32F2: 2.2.0
+  * STM32F3: 2.3.1
+  * STM32F4: 2.6.1
+  * STM32F7: 1.2.0
+  * STM32L0: 1.7.1
+  * STM32L1: 2.2.1
+  * STM32L4: 1.3.1
+
+Release notes of each STM32YYxx CMSIS available here:
+
+`system/Drivers/CMSIS/Device/ST/STM32YYxx/Release_Notes.html`
+
+Where 'YY' is the STM32 MCU series.