Config: Add stm targets in single entry point

This patch allows to group all stm targets in single cmake entry point.
The stm TARGET_PLATFORM should prefix by "STM".
stm platforms supports CoreIPC, CoreIPCTfmLevel2 and RegressionIPCTfmLevel2
Build with GNUARM toolchain.

Change-Id: I6535420b2304c18f2ab260620c38fef632eb7488
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Michel Jaouen <michel.jaouen@st.com>
11 files changed