Add dreambox-buildimage to OPTIONAL_BSP_PACKAGES

Signed-off-by: Erik Slagter <erik@openpli.org>
xtrend: update bsp

commit 61e9b14
Author: xtrendmaster <amicimax@aol.com>
Date:   Tue Dec 23 12:57:21 2014 +0000

    [ET8500] Enable Real Multiboot OS
Merge branch 'master' of git://git.code.sf.net/p/openpli/openpli-oe-core