IB/hfi1: Fix a subcontext memory leak

The only context that frees user_exp_rcv data structures is the last
context closed (from a sub-context set).  This leaks the allocations
from the other sub-contexts.  Separate the common frees from the
specific frees and call them at the appropriate time.

Using KEDR to check for memory leaks we get:

Before test:

[leak_check] Possible leaks: 25

After test:

[leak_check] Possible leaks: 31  (6 leaked data structures)

After patch applied (before and after test have the same value)

[leak_check] Possible leaks: 25

Each leak is 192 + 13440 + 6720 = 20352 bytes per sub-context.

Cc: stable@vger.kernel.org
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>