IB/mthca: Fix buddy->num_free allocation size

The num_free field of mthca_buddy has a type of array of unsigned int
while it was allocated as an array of pointers.  On 64-bit platforms
this allocates twice more than required.  Fix this by allocating the
correct size for the type.

This is the same bug just fixed in mlx4 by Eli Cohen <eli@mellanox.co.il>.
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mthca/mthca_mr.c

@@ -146,7 +146,7 @@ static int mthca_buddy_init(struct mthca_buddy *buddy, int max_order)
 
 	buddy->bits = kzalloc((buddy->max_order + 1) * sizeof (long *),
 			      GFP_KERNEL);
-	buddy->num_free = kzalloc((buddy->max_order + 1) * sizeof (int *),
+	buddy->num_free = kcalloc((buddy->max_order + 1), sizeof *buddy->num_free,
 				  GFP_KERNEL);
 	if (!buddy->bits || !buddy->num_free)
 		goto err_out;