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/CZ.NIC/turris_omnia/turris_omnia.c b/board/CZ.NIC/turris_omnia/turris_omnia.c
index 1f7650c..c7f6479 100644
--- a/board/CZ.NIC/turris_omnia/turris_omnia.c
+++ b/board/CZ.NIC/turris_omnia/turris_omnia.c
@@ -365,7 +365,7 @@
 #endif
 
 #if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_WDT_ORION)
-static struct udevice *watchdog_dev = NULL;
+static struct udevice *watchdog_dev __attribute__((section(".data"))) = NULL;
 #endif
 
 int board_init(void)