IB: Make sure struct ib_user_mad.data is aligned

Make the untyped data region in ib_user_mad have type u64 so that it
gets aligned properly. This avoids alignment faults in ib_umad when
casting the data field to an rmpp_mad and accessing the 64-bit tid
field on architectures like ia64.

Signed-off-by: Jason Gunthorpe <[e-mail]>
Signed-off-by: Roland Dreier <[e-mail]>

include/rdma/ib_user_mad.h

···
  */
 struct ib_user_mad {
 	struct ib_user_mad_hdr hdr;
-	__u8	data[0];
+	__u64	data[0];
 };
 
 /**