aboot: Fix issue with secure boot

For secure boot signature is appended at the end of
kernel image. With device tree support ramdisk size is
added as dt size while calculating actual image size
of kernel. This breaks secure boot for targets which
do not use device tree. Use dt size only if device tree
is supported.

Change-Id: I1302c71a1eb3283ac18135397f25fa7d58fd93bb
1 file changed