GCC47: Fix warning in cmd_nand.c

cmd_nand.c: In function ‘arg_off_size’:
cmd_nand.c:216:5: warning: ‘maxsize’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Wolfgang Denk <wd@denx.de>

common/cmd_nand.c

@@ -191,7 +191,7 @@ static int arg_off_size(int argc, char *const argv[], int *idx,
 			loff_t *off, loff_t *size)
 {
 	int ret;
-	loff_t maxsize;
+	loff_t maxsize = 0;
 
 	if (argc == 0) {
 		*off = 0;