Platform/DeveloperBox: add 96boards/Socionext logo

Add a nice splash screen with the Socionext and 96boards logos.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>