dfu:function: Fix number of allocated DFU function pointers

This subtle change fix problem with too small amount of allocated
memory to store DFU function pointers.

One needs to allocate extra space for sentinel NULL pointer in this array
of function pointers.

With the previous code, the NULL value overwrites malloc internal data
and afterwards free(f_dfu->function) crashes.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Vasut <marex@denx.de>

drivers/usb/gadget/f_dfu.c

@@ -589,7 +589,7 @@ static int dfu_prepare_function(struct f_dfu *f_dfu, int n)
 	struct usb_interface_descriptor *d;
 	int i = 0;
 
-	f_dfu->function = calloc(sizeof(struct usb_descriptor_header *), n);
+	f_dfu->function = calloc(sizeof(struct usb_descriptor_header *), n + 1);
 	if (!f_dfu->function)
 		goto enomem;