board/zynq/post-image.sh: correct comment text

Signed-off-by: Neal Frager <neal.frager@amd.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

board/zynq/post-image.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# By default U-Boot loads DTB from a file named "devicetree.dtb", so
+# By default U-Boot loads DTB from a file named "system.dtb", so
 # let's use a symlink with that name that points to the *first*
 # devicetree listed in the config.