ide: make drive->id an union (take 2)

Make drive->id an unnamed union so id can be accessed either by using
'u16 *id' or 'struct hd_driveid *driveid'.  Then convert all existing
drive->id users accordingly (using 'u16 *id' when possible).

This is an intermediate step to make ide 'struct hd_driveid'-free.

While at it:

- Add missing KERN_CONTs in it821x.c.

- Use ATA_ID_WORDS and ATA_ID_*_LEN defines.

- Remove unnecessary checks for drive->id.

- s/drive_table/table/ in ide_in_drive_list().

- Cleanup ide_config_drive_speed() a bit.

- s/drive1/dev1/ & s/drive0/dev0/ in ide_undecoded_slave().

v2:
Fix typo in drivers/ide/ppc/pmac.c. (From Stephen Rothwell)

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index a373cc4..2c4c667 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -2311,7 +2311,7 @@
 	if (drive->id_read == 0)
 		return 1;
 
-	*((unsigned short *) &gcw) = drive->id->config;
+	*((u16 *)&gcw) = drive->id[ATA_ID_CONFIG];
 
 	protocol	=   (gcw[1] & 0xC0) >> 6;
 	device_type	=    gcw[1] & 0x1F;
@@ -2463,7 +2463,7 @@
 		drive->dsc_overlap = 0;
 	}
 	/* Seagate Travan drives do not support DSC overlap. */
-	if (strstr(drive->id->model, "Seagate STT3401"))
+	if (strstr((char *)&drive->id[ATA_ID_PROD], "Seagate STT3401"))
 		drive->dsc_overlap = 0;
 	tape->minor = minor;
 	tape->name[0] = 'h';
@@ -2471,7 +2471,8 @@
 	tape->name[2] = '0' + minor;
 	tape->chrdev_dir = IDETAPE_DIR_NONE;
 	tape->pc = tape->pc_stack;
-	*((unsigned short *) &gcw) = drive->id->config;
+
+	*((u16 *)&gcw) = drive->id[ATA_ID_CONFIG];
 
 	/* Command packet DRQ type */
 	if (((gcw[0] & 0x60) >> 5) == 1)