watchdog: Move watchdog_dev to data section (BSS may not be cleared)

This patch moves all instances of static "watchdog_dev" declarations to
the "data" section. This may be needed, as the BSS may not be cleared
in the early U-Boot phase, where watchdog_reset() is already beeing
called. This may result in incorrect pointer access, as the check to
"!watchdog_dev" in watchdog_reset() may not be true and the function
may continue to run.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "Marek BehĂșn" <marek.behun@nic.cz>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Tested-by: Michal Simek <michal.simek@xilinx.com> (on zcu100)
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynq/board.c b/board/xilinx/zynq/board.c
index b4b84df..ea26aad 100644
--- a/board/xilinx/zynq/board.c
+++ b/board/xilinx/zynq/board.c
@@ -19,17 +19,12 @@
 DECLARE_GLOBAL_DATA_PTR;
 
 #if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_WDT)
-static struct udevice *watchdog_dev;
+static struct udevice *watchdog_dev __attribute__((section(".data"))) = NULL;
 #endif
 
 #if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_BOARD_EARLY_INIT_F)
 int board_early_init_f(void)
 {
-# if defined(CONFIG_WDT)
-	/* bss is not cleared at time when watchdog_reset() is called */
-	watchdog_dev = NULL;
-# endif
-
 	return 0;
 }
 #endif