ARM: omap3_logic: Enable SPL booting device tree

With the generic omap3-u-boot.dtsi file available, this patch
increased the memory of the various incarnations of the omap3_logic
board, and points their respective u-boot.dtsi files to the newly
created generic one, and removes the PLATDATA from the board file.

These are all done at once because the're all utilizing the same
omap3logic.c board file.

Signed-off-by: Adam Ford <aford173@gmail.com>