target: Add workaround for zero-length control CDB handling
This patch adds a work-around for handling zero allocation length
control CDBs (type SCF_SCSI_CONTROL_SG_IO_CDB) that was causing an
OOPs with the following raw calls:
This patch will follow existing zero-length handling for data I/O
and silently return with GOOD status. This addresses the zero length
issue, but the proper long-term resolution for handling arbitary
allocation lengths will be to refactor out data-phase handling in
individual CDB emulation logic within target_core_cdb.c
Reported-by: Roland Dreier <roland@purestorage.com> Cc: <stable@vger.kernel.org> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>