Only compile Xilinx Bootgen when building Zynq based image

config/sources/families/zynq.conf

@@ -23,8 +23,12 @@ family_tweaks()
 uboot_custom_postprocess()
 {
 	# Precompiled first stage bootloader
+	(fetch_from_repo "https://github.com/tparys/xilinx-fsbl-blobs" "xilinx-fsbl" "branch:master")
 	cp ${SRC}/cache/sources/xilinx-fsbl/zynq/fsbl.elf .
 
+	# Compile Xilinx bootgen to make boot image
+	compile_xilinx_bootgen
+
 	# Create a bootgen build instruction file
     	cat > build.bif <<EOF
 the_ROM_image : {