ARM: dts: stm32: split sdram pin & timing parameter into specific board dts

ARM: dts: stm32: split sdram pin & timing parameter into specific board dts

As different boards has their own sdram hw connection, mount different
sdram modules, so move sdram timing parameter and pin configuration
to their board device tree.

Signed-off-by: dillon min <dillon.minfei@gmail.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>