greybus: zero all data buffers

Don't assume the buffer data area will all be overwritten.  Zero all
buffer space, to avoid sending crap over the wire.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/es1-ap-usb.c

@@ -113,7 +113,7 @@ static int alloc_gbuf_data(struct gbuf *gbuf, unsigned int size,
 	 * CPort Id before the data; set aside an extra byte for
 	 * that purpose in that case.
 	 */
-	buffer = kmalloc(cport_reserve + size, gfp_mask);
+	buffer = kzalloc(cport_reserve + size, gfp_mask);
 	if (!buffer)
 		return -ENOMEM;