ARM: ux500: enable appended dtb in u8500_defconfig

Churns the rest of the file a bit due to reordering of options, but the
only changes are:

CONFIG_ARM_APPENDED_DTB=y
CONFIG_ARM_ATAG_DTB_COMPAT=y

Signed-off-by: Olof Johansson <olof@lixom.net>