fdts: stm32mp1: add IO policies into BL2 device tree

Add the UUID into the io policies node that are retrieved
by BL2 using stm32mp_fconf_io.c populate function.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: I595d5a41a1e0a27fcc02ea2ab5495d9dbf0e6773
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/178509


Reviewed-by: Yann GAUTIER <yann.gautier@st.com>
Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>