drivers/video: fsl-diu-fb: set the driver name to "fsl-diu-fb"

Use the name "fsl-diu-fb" in the Freescale DIU framebuffer driver
during registrations.

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