mfd: viperboard: Do version query in dma memory

The query for the viperboard version was done with memory buffer
on the stack but usb transfers need dma capable memory buffer.
This is fixed now.

Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c
index 276122b..af2a670 100644
--- a/drivers/mfd/viperboard.c
+++ b/drivers/mfd/viperboard.c
@@ -56,7 +56,6 @@
 
 	u16 version = 0;
 	int pipe, ret;
-	unsigned char buf[1];
 
 	/* allocate memory for our device state and initialize it */
 	vb = kzalloc(sizeof(*vb), GFP_KERNEL);
@@ -76,17 +75,17 @@
 	/* get version information, major first, minor then */
 	pipe = usb_rcvctrlpipe(vb->usb_dev, 0);
 	ret = usb_control_msg(vb->usb_dev, pipe, VPRBRD_USB_REQUEST_MAJOR,
-		VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, buf, 1,
+		VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, vb->buf, 1,
 		VPRBRD_USB_TIMEOUT_MS);
 	if (ret == 1)
-		version = buf[0];
+		version = vb->buf[0];
 
 	ret = usb_control_msg(vb->usb_dev, pipe, VPRBRD_USB_REQUEST_MINOR,
-		VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, buf, 1,
+		VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, vb->buf, 1,
 		VPRBRD_USB_TIMEOUT_MS);
 	if (ret == 1) {
 		version <<= 8;
-		version = version | buf[0];
+		version = version | vb->buf[0];
 	}
 
 	dev_info(&interface->dev,