bimgtool: initialize data header

Otherwise dummy contains uninitialized data, which leads to non-reproducible
builds (and a leak of 4 bytes of stack data).

Change-Id: Iaaf846580ec436fdd4f0800c7576b544f50d6ae0
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10524
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed