fix(stm32mp1-fdts): move /omit-if-no-ref/ to overlay files

To keep (as much as possible) alignment with Linux DT, move the
/omit-if-no-ref/ keywords to DT overlay files (fdts/stm32mp1*-bl*.dtsi).
This also ease checks for ST tools.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: Ib467a6b65f05a84c9678799ad32e1820249b4ed1
5 files changed