Factor out common parts of STM32MP15xx DRAM controller configuration DT
description into stm32mp1-ddr.dtsi and introduce stm32mp13-ddr.dtsi which
describes STM32MP13xx DRAM controller configuration in DT.
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Marek Vasut <marek.vasut@mailbox.org>
