board/BuR/common: remove BMP_DISPLAY from tseries board

Since we display in future the splash screen out of linux-os, we don't need
this support anymore within the common section.

But kwb-target is still using BMP_DISPLAY feature, so we move the related
from the common section into the target-specific.

Also the default environment of tseries will be adapted to this.

Signed-off-by: Hannes Petermaier <oe5hpm@oevsv.at>