nitrogen6x: display: add svga display (800x600)

Add support for 800x600 18-bit RGB displays using VESA GTF timings.

No auto-detection is supported, so you must configure this panel
manually through the 'panel' environment variable:

        U-Boot > setenv panel svga
        U-Boot > saveenv && reset

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
1 file changed