arm: ti: logicpd-som-lv: Migrate to OF_UPSTREAM

The DM37 and OMAP35 SOM-LV share a few files, but both of them
can be migrated to OF_UPSTREAM with a small update to their
respective u-boot.dtsi files to address changes made the aliases.
Both defconfigs need to properly point to the upstream directory
structure for the device trees.  With those updated, the U-Boot
device tree files can be deleted.

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

V2:  Remove DT from Makefile