target/sbc: Make internal DIF emulation honor ->prot_checks
The internal DIF emulation was not honoring se_cmd->prot_checks for
the WRPROTECT/RDPROTECT == 0x3 case, so sbc_dif_v1_verify() has been
updated to follow which checks have been calculated based on
WRPROTECT/RDPROTECT in sbc_set_prot_op_checks().
Reviewed-by: Martin Petersen <martin.petersen@oracle.com> Reviewed-by: Sagi Grimberg <sagig@mellanox.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>