target: Fail I/O with PROTECT bit when protection is unsupported
This patch adds an explicit check for WRPROTECT + RDPROTECT bit usage
within sbc_check_prot(), and fails with TCM_INVALID_CDB_FIELD if the
backend device does not have protection enabled.
Also, update sbc_check_prot() to return sense_reason_t in order to
propigate up the correct sense ASQ.
Cc: Martin Petersen <martin.petersen@oracle.com> Cc: Sagi Grimberg <sagig@mellanox.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>