mfd: tps65910: Delete an unnecessary variable initialisation in tps65910_sleepinit()

The local variable "dev" will be reassigned by a following statement.
Thus omit the explicit initialisation at the beginning.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/tps65910.c

@@ -312,7 +312,7 @@ static int tps65910_ck32k_init(struct tps65910 *tps65910,
 static int tps65910_sleepinit(struct tps65910 *tps65910,
 		struct tps65910_board *pmic_pdata)
 {
-	struct device *dev = NULL;
+	struct device *dev;
 	int ret;
 
 	dev = tps65910->dev;