IB/mthca: Increase max number of QPs per multicast group to 56

Increase the number of QPs allowed per multicast group from 8 to 56.
This allows for one QP per core on 16-core systems, which are now
quite common, and allows some space for future growth.

This is basically the same patch that Jack Morgenstein
<jackm@dev.mellanox.co.il> just supplied for mlx4.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_dev.h

@@ -83,7 +83,7 @@ enum {
 	MTHCA_QP_CONTEXT_SIZE = 0x200,
 	MTHCA_RDB_ENTRY_SIZE  =  0x20,
 	MTHCA_AV_SIZE         =  0x20,
-	MTHCA_MGM_ENTRY_SIZE  =  0x40,
+	MTHCA_MGM_ENTRY_SIZE  = 0x100,
 
 	/* Arbel FW gives us these, but we need them for Tavor */
 	MTHCA_MPT_ENTRY_SIZE  =  0x40,