packet-usb-audio.c: Trivial changes

- Remove unneeded #include;
- Remove some trailing whitespace;

Change-Id: Iddf137d1d507dea4e3e892831fe6a05b80d2fa50
Reviewed-on: https://code.wireshark.org/review/3620
Reviewed-by: Bill Meier <wmeier@newsguy.com>

epan/dissectors/packet-usb-audio.c

@@ -25,9 +25,8 @@
 #include "config.h"
 
 #include <glib.h>
-#include <epan/conversation.h>
-#include <epan/expert.h>
 #include <epan/packet.h>
+#include <epan/expert.h>
 #include <epan/reassemble.h>
 #include "packet-usb.h"