arm: zynq: Add missing watchdog header

Add missing header detected by sparse.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynq/board.c b/board/xilinx/zynq/board.c
index e4f86d1..1106f5c 100644
--- a/board/xilinx/zynq/board.c
+++ b/board/xilinx/zynq/board.c
@@ -9,6 +9,7 @@
 #include <fdtdec.h>
 #include <fpga.h>
 #include <mmc.h>
+#include <watchdog.h>
 #include <wdt.h>
 #include <zynqpl.h>
 #include <asm/arch/hardware.h>