fb: port to am335x (work-in-progress)

 * split DM37XX specific code into it's own file.

Change-Id: I0dbc345c3bf7500b181f02f06376d2d09c860585
splash: framebuffer test program

Change-Id: I7e045a4c6cec476615057f46f530693c0a2a17e0
splash: use parameters provided by the fb driver

Certain parameters, such as screen resolution, differ between
monitors. Enhance the splash program to dynamically configure
itself.

Change-Id: I49b0a3704decb7cb4633a1ee424b0419a1d67cf0