ide: remove ide_drive_t.usage

This field is no longer used by the core IDE code so fix ide-{disk,floppy}
drivers to keep openers count in the driver specific objects and remove
it from ide-{cd,scsi,tape} drivers (it was write-only).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 0a05a37..e2cea18 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -77,6 +77,7 @@
 	ide_driver_t	*driver;
 	struct gendisk	*disk;
 	struct kref	kref;
+	unsigned int	openers;	/* protected by BKL for now */
 };
 
 static DEFINE_MUTEX(idedisk_ref_mutex);
@@ -1081,8 +1082,9 @@
 
 	drive = idkp->drive;
 
-	drive->usage++;
-	if (drive->removable && drive->usage == 1) {
+	idkp->openers++;
+
+	if (drive->removable && idkp->openers == 1) {
 		ide_task_t args;
 		memset(&args, 0, sizeof(ide_task_t));
 		args.tfRegister[IDE_COMMAND_OFFSET] = WIN_DOORLOCK;
@@ -1106,9 +1108,10 @@
 	struct ide_disk_obj *idkp = ide_disk_g(disk);
 	ide_drive_t *drive = idkp->drive;
 
-	if (drive->usage == 1)
+	if (idkp->openers == 1)
 		ide_cacheflush_p(drive);
-	if (drive->removable && drive->usage == 1) {
+
+	if (drive->removable && idkp->openers == 1) {
 		ide_task_t args;
 		memset(&args, 0, sizeof(ide_task_t));
 		args.tfRegister[IDE_COMMAND_OFFSET] = WIN_DOORUNLOCK;
@@ -1117,7 +1120,8 @@
 		if (drive->doorlocking && ide_raw_taskfile(drive, &args, NULL))
 			drive->doorlocking = 0;
 	}
-	drive->usage--;
+
+	idkp->openers--;
 
 	ide_disk_put(idkp);