IB/mthca: Fix data corruption after FMR unmap on Sinai

In mthca_arbel_fmr_unmap(), the high bits of the key are masked off.
This gets rid of the effect of adjust_key(), which makes sure that
bits 3 and 23 of the key are equal when the Sinai throughput
optimization is enabled, and so it may happen that an FMR will end up
with bits 3 and 23 in the key being different.  This causes data
corruption, because when enabling the throughput optimization, the
driver promises the HCA firmware that bits 3 and 23 of all memory keys
will always be equal.

Fix by re-applying adjust_key() after masking the key.

Thanks to Or Gerlitz for reproducing the problem, and Ariel Shahar for
help in debug.
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_mr.c

@@ -835,6 +835,7 @@ void mthca_arbel_fmr_unmap(struct mthca_dev *dev, struct mthca_fmr *fmr)
 
 	key = arbel_key_to_hw_index(fmr->ibmr.lkey);
 	key &= dev->limits.num_mpts - 1;
+	key = adjust_key(dev, key);
 	fmr->ibmr.lkey = fmr->ibmr.rkey = arbel_hw_index_to_key(key);
 
 	fmr->maps = 0;