uboot-phytec

vexpress_ca9x4: Enable use of correct DTB file and restore EFI loader.

EFI was disabled in f95b8a4b5f64f because of the missing DTB file,
and indeed, the DTB file is required to load recent versions of GRUB
(2.04) correctly.

Signed-off-by: Kristian Amlie <kristian.amlie@northern.tech>