drivers/video: fsl-diu-fb: move some definitions out of the header file

Move several macros and structures from the Freescale DIU driver's header
file into the source file, because they're only used by that file.  Also
delete a few unused macros.

The diu and diu_ad structures cannot be moved because they're being used
by the MPC5121 platform file.  A future patch eliminate the need for
the platform file to access these structs, so they'll be moved also.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>