libata: const-ification bombing run

Enforce access rules where appropriate.

If the compiler is smart enough, this may buy us an optimization or two
as a side effect.
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 90bf222..5885888 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -44,9 +44,9 @@
 
 #include "libata.h"
 
-typedef unsigned int (*ata_xlat_func_t)(struct ata_queued_cmd *qc, u8 *scsicmd);
+typedef unsigned int (*ata_xlat_func_t)(struct ata_queued_cmd *qc, const u8 *scsicmd);
 static struct ata_device *
-ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev);
+ata_scsi_find_dev(struct ata_port *ap, const struct scsi_device *scsidev);
 
 
 static void ata_scsi_invalid_field(struct scsi_cmnd *cmd,
@@ -418,7 +418,7 @@
  */
 
 static unsigned int ata_scsi_start_stop_xlat(struct ata_queued_cmd *qc,
-					     u8 *scsicmd)
+					     const u8 *scsicmd)
 {
 	struct ata_taskfile *tf = &qc->tf;
 
@@ -485,7 +485,7 @@
  *	Zero on success, non-zero on error.
  */
 
-static unsigned int ata_scsi_flush_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
+static unsigned int ata_scsi_flush_xlat(struct ata_queued_cmd *qc, const u8 *scsicmd)
 {
 	struct ata_taskfile *tf = &qc->tf;
 
@@ -512,7 +512,7 @@
  *	@plen: the transfer length
  */
 
-static void scsi_6_lba_len(u8 *scsicmd, u64 *plba, u32 *plen)
+static void scsi_6_lba_len(const u8 *scsicmd, u64 *plba, u32 *plen)
 {
 	u64 lba = 0;
 	u32 len = 0;
@@ -539,7 +539,7 @@
  *	@plen: the transfer length
  */
 
-static void scsi_10_lba_len(u8 *scsicmd, u64 *plba, u32 *plen)
+static void scsi_10_lba_len(const u8 *scsicmd, u64 *plba, u32 *plen)
 {
 	u64 lba = 0;
 	u32 len = 0;
@@ -569,7 +569,7 @@
  *	@plen: the transfer length
  */
 
-static void scsi_16_lba_len(u8 *scsicmd, u64 *plba, u32 *plen)
+static void scsi_16_lba_len(const u8 *scsicmd, u64 *plba, u32 *plen)
 {
 	u64 lba = 0;
 	u32 len = 0;
@@ -608,7 +608,7 @@
  *	Zero on success, non-zero on error.
  */
 
-static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
+static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, const u8 *scsicmd)
 {
 	struct ata_taskfile *tf = &qc->tf;
 	struct ata_device *dev = qc->dev;
@@ -734,7 +734,7 @@
  *	Zero on success, non-zero on error.
  */
 
-static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
+static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, const u8 *scsicmd)
 {
 	struct ata_taskfile *tf = &qc->tf;
 	struct ata_device *dev = qc->dev;
@@ -1688,7 +1688,7 @@
  *	Zero on success, non-zero on failure.
  */
 
-static unsigned int atapi_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
+static unsigned int atapi_xlat(struct ata_queued_cmd *qc, const u8 *scsicmd)
 {
 	struct scsi_cmnd *cmd = qc->scsicmd;
 	struct ata_device *dev = qc->dev;
@@ -1757,7 +1757,7 @@
  */
 
 static struct ata_device *
-ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev)
+ata_scsi_find_dev(struct ata_port *ap, const struct scsi_device *scsidev)
 {
 	struct ata_device *dev;
 
@@ -1914,7 +1914,7 @@
 		      void (*done)(struct scsi_cmnd *))
 {
 	struct ata_scsi_args args;
-	u8 *scsicmd = cmd->cmnd;
+	const u8 *scsicmd = cmd->cmnd;
 
 	args.id = id;
 	args.cmd = cmd;