[PATCH] IB: Keep MAD work completion valid

Replace the *wc field in ib_mad_recv_wc from pointing to a structure on the
stack to one allocated with the received MAD buffer.  This allows a client to
access the *wc field after their receive completion handler has returned.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>