[SCSI] gdth: !use_sg cleanup and use of scsi accessors

gdth_execute() will issue an internal, none scsi-standard commands
onto __gdth_queuecommand(). Since it is not recommended to set
struct scsi_cmnd IO members in llds, gdth now uses internal IO
members for IO. In the case of gdth_execute() these members will be
set properly. In case the command was issued from scsi-ml
(by gdth_queuecommand) they will be set from scsi IO accessors.

  * define gdth IO accessors and use them throughout the driver.
  * use an sg-of-one in gdth_execute() and fix gdth_special_cmd()
    accordingly.
  * Clean the not use_sg code path and company

Signed-off-by Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/gdth.h

@@ -303,15 +303,8 @@
 #define MAILBOXREG      0x0c90                  /* mailbox reg. (16 bytes) */
 #define EISAREG         0x0cc0                  /* EISA configuration */
 
-/* DMA memory mappings */
-#define GDTH_MAP_NONE   0
-#define GDTH_MAP_SINGLE 1
-#define GDTH_MAP_SG     2
-#define GDTH_MAP_IOCTL  3 
-
 /* other defines */
 #define LINUX_OS        8                       /* used for cache optim. */
-#define SCATTER_GATHER  1                       /* s/g feature */
 #define SECS32          0x1f                    /* round capacity */
 #define BIOS_ID_OFFS    0x10                    /* offset contr-ID in ISABIOS */
 #define LOCALBOARD      0                       /* board node always 0 */