ARM: dts: stm32: convert stm32mp2 board to OF_UPSTREAM

Enable OF_UPSTREAM flag for STM32MP2 platforms.
Add fixed-clock ck_flexgen_08 and ck_icn_ls_mcu until STM32MP25
clock driver will be available.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
15 files changed