After introducing the new STM32MP1 SoC versions in patch [1], the
document describing STM32MP1 platform is updated with the information
given in the patch commit message.

 [1]: stm32mp1: add support for new SoC profiles

Change-Id: I6d7ce1a3c29678ddac78a6685f5d5daf28c3c3a1
Signed-off-by: Yann Gautier <yann.gautier@st.com>