tools: zynqmpimage: adjust ug1085 reference to v1.4 of the document

The chapter in which the table explaining the image format changed
chapter as the document evolved. This should help people track the
info down faster.

Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>