Commit bed8bdfd ("IB: kmemdup() cleanup") introduced one bad conversion to
kmemdup() in mthca_alloc_fmr(), where the structure allocated and the
structure copied are not the same size.  Revert this back to the original
kmalloc()/memcpy() code.

Reported-by: Dotan Barak <dotanb@mellanox.co.il>.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <roland@digitalvampire.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>