docs(changelog): add subsections for STM32MP2

Now that STM32MP2 family has different types of SoCs, add relative
subsections for STM32MP2. The same is done for FDTS scopes.

Change-Id: I374215c44ce9515ca33b5882058a71db4886b80a
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>
1 file changed