Revert "IPoIB: fix MCAST_FLAG_BUSY usage"

This reverts commit 016d9fb2.

The series of IPoIB bug fixes that went into 3.19-rc1 introduce
regressions, and after trying to sort things out, we decided to revert
to 3.18's IPoIB driver and get things right for 3.20.
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -98,15 +98,9 @@ enum {
 
 	IPOIB_MCAST_FLAG_FOUND	  = 0,	/* used in set_multicast_list */
 	IPOIB_MCAST_FLAG_SENDONLY = 1,
-	/*
-	 * For IPOIB_MCAST_FLAG_BUSY
-	 * When set, in flight join and mcast->mc is unreliable
-	 * When clear and mcast->mc IS_ERR_OR_NULL, need to restart or
-	 *   haven't started yet
-	 * When clear and mcast->mc is valid pointer, join was successful
-	 */
-	IPOIB_MCAST_FLAG_BUSY	  = 2,
+	IPOIB_MCAST_FLAG_BUSY	  = 2,	/* joining or already joined */
 	IPOIB_MCAST_FLAG_ATTACHED = 3,
+	IPOIB_MCAST_JOIN_STARTED  = 4,
 
 	MAX_SEND_CQE		  = 16,
 	IPOIB_CM_COPYBREAK	  = 256,