[WATCHDOG] pcwd.c - fix open_allowed type.

Fix following warnings:
drivers/watchdog/pcwd.c: In function 'pcwd_open':
drivers/watchdog/pcwd.c:703: warning: passing argument 2 of 'test_and_set_bit' from incompatible pointer type
drivers/watchdog/pcwd.c: In function 'pcwd_close':
drivers/watchdog/pcwd.c:723: warning: passing argument 2 of 'clear_bit' from incompatible pointer type

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/pcwd.c

@@ -168,7 +168,7 @@ static const int heartbeat_tbl[] = {
 static int cards_found;
 
 /* internal variables */
-static atomic_t open_allowed = ATOMIC_INIT(1);
+static unsigned long open_allowed;
 static char expect_close;
 static int temp_panic;