target/sbc: Fix sbc_dif_verify inconsistent map/unmap
target/sbc: Fix sbc_dif_verify inconsistent map/unmap

Fix map/unmap consistency and get rid of a redundant
local variable psg.

Reported-by: Akinobu Mita <3807cf899f217da549814bf6c330d3b6e6819ccf@gmail.com>
Signed-off-by: Sagi Grimberg <380ce2a82d3d08e67ab163b51dc6d30288ad3f13@mellanox.com>
Signed-off-by: Nicholas Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs