Handle minimalistic boot images

At a minimum a boot image consists of boot header and FSBL only,
omitting image-, partition headers etc. Handle such cases correctly.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Remove TODO

The todo items are done.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Allow dumping of boot header

Since image- and partition headers are optional, allow the dump
operation on the boot header.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>