[libata] replace ATA_QCFLAG_ATAPI with inline helper

Detection of an ATAPI taskfile is possible using a simple test
on existing information, so there is no need to cache this value
in a separate flag (ATA_QCFLAG_ATAPI).  Instead, create and use
a new helper function is_atapi_taskfile().

drivers/scsi/libata-core.c

@@ -2321,7 +2321,7 @@ void ata_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
 
 	if (cmd) {
 		if (unlikely(drv_stat & (ATA_ERR | ATA_BUSY | ATA_DRQ))) {
-			if (qc->flags & ATA_QCFLAG_ATAPI)
+			if (is_atapi_taskfile(&qc->tf))
 				cmd->result = SAM_STAT_CHECK_CONDITION;
 			else
 				ata_to_sense_error(qc);

drivers/scsi/libata-scsi.c

@@ -951,8 +951,6 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 {
 	struct scsi_cmnd *cmd = qc->scsicmd;
 
-	qc->flags |= ATA_QCFLAG_ATAPI;
-
 	qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
 	if (cmd->sc_data_direction == SCSI_DATA_WRITE) {
 		qc->tf.flags |= ATA_TFLAG_WRITE;

include/linux/ata.h

@@ -218,4 +218,10 @@ struct ata_taskfile {
 	  ((u64) dev->id[(n) + 1] << 16) |	\
 	  ((u64) dev->id[(n) + 0]) )
 
+static inline int is_atapi_taskfile(struct ata_taskfile *tf)
+{
+	return (tf->protocol == ATA_PROT_ATAPI) ||
+	       (tf->protocol == ATA_PROT_ATAPI_DMA);
+}
+
 #endif /* __LINUX_ATA_H__ */

include/linux/libata.h

@@ -111,7 +111,6 @@ enum {
 
 	ATA_QCFLAG_ACTIVE	= (1 << 1), /* cmd not yet ack'd to scsi lyer */
 	ATA_QCFLAG_DMA		= (1 << 2), /* data delivered via DMA */
-	ATA_QCFLAG_ATAPI	= (1 << 3), /* is ATAPI packet command? */
 	ATA_QCFLAG_SG		= (1 << 4), /* have s/g table? */
 
 	/* various lengths of time */