[SCSI] sd: make printing use a common prefix

Make SCSI disk printing more consistent:

 - Define sd_printk(), sd_print_sense_hdr() and sd_print_result()

 - Move relevant header bits into sd.h

 - Remove all the legacy disk_name passing and use scsi_disk pointers
   where possible

 - Switch printk() lines to the new sd_ functions so that output is
   consistent

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>