Dockerfile: install xilinx-bootgen package

Bootgen is used in a binman test. The test is skipped without the binary.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/tools/docker/Dockerfile b/tools/docker/Dockerfile
index 30cda72..dae6c24 100644
--- a/tools/docker/Dockerfile
+++ b/tools/docker/Dockerfile
@@ -116,6 +116,7 @@
 	virtualenv \
 	vboot-kernel-utils \
 	vboot-utils \
+	xilinx-bootgen \
 	xxd \
 	zip \
 	&& rm -rf /var/lib/apt/lists/*