rt2x00: Optimize rt2x00debug_dump_frame when frame dumping is not active

When rt2x00 is compiled with debugging but frame dumping is currently
not active we can avoid the call to do_gettimeofday. Furthermore,
frame dumping is not the default case, mark it as unlikely.
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00debug.c

@@ -162,11 +162,11 @@ void rt2x00debug_dump_frame(struct rt2x00_dev *rt2x00dev,
 	struct timeval timestamp;
 	u32 data_len;
 
-	do_gettimeofday(&timestamp);
-
-	if (!test_bit(FRAME_DUMP_FILE_OPEN, &intf->frame_dump_flags))
+	if (likely(!test_bit(FRAME_DUMP_FILE_OPEN, &intf->frame_dump_flags)))
 		return;
 
+	do_gettimeofday(&timestamp);
+
 	if (skb_queue_len(&intf->frame_dump_skbqueue) > 20) {
 		DEBUG(rt2x00dev, "txrx dump queue length exceeded.\n");
 		return;