IB/mad: Fix kernel crash when .process_mad() returns SUCCESS|CONSUMED

If a low-level driver returns IB_MAD_RESULT_SUCCESS | IB_MAD_RESULT_CONSUMED,
handle_outgoing_dr_smp() doesn't clean up properly.  The fix is to
kfree the local data and break, rather than falling through.  This was
observed with the ipath driver, but could happen with any driver.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=1027>.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>