fix(stm32mp1-fdts): re-enable RTC clock

On STM32MP15 ST boards, RTC clock configuration by OPTEE is not ready
yet. Re-enable it temporary to get LSE as clock source of RTC.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Change-Id: Ib6071229552e456faffb4fdfc8db9808140d54a7
2 files changed