arm: am437x: cm-t43: Add device tree, enable OF_CONTROL

Add device tree from Linux for driver model conversion
and enable OF_CONTROL. This will remove the following compile
warning:
==================================================
Device Tree Source is not correctly specified.
Please define 'CONFIG_DEFAULT_DEVICE_TREE'
or build with 'DEVICE_TREE=<device_tree>' argument
===================================================
Target was compile tested, build was clean.

Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>