ARM: dts: exynos7870-j6lte: add properties to make S-BOOT happy

ARM: dts: exynos7870-j6lte: add properties to make S-BOOT happy

Add properties in the DTSI file which is required for S-BOOT when used
an external device tree when booting into U-Boot. S-BOOT is Samsung's
proprietary bootloader, which chainloads U-Boot.

Since this device has multiple bank nodes, add memory nodes for each RAM
bank. This is the format S-BOOT recognizes, and (re)populates it with
the correct bank sizes.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>