[SCSI] raid_attrs: fix dependency problems

RAID attributes uses scsi_is_sdev_device() to gate some SCSI specific
checking code. This causes two problems. Firstly if SCSI == n just
defining scsi_is_sdev_device() to return false might not be enough to
prevent gcc from emitting the code (and thus referring to undefined
symbols), so this needs surrounding with an ifdef. Secondly, using
scsi_is_sdev_device() when SCSI is either y or m gives a subtle
problem in the m case: raid_attrs must also be m to use the symbol.
Do the usual Kconfig jiggery-pokery to fix this.

Reported-by: Randy Dunlap <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/Kconfig

···
 menu "SCSI device support"
 
+config SCSI_MOD
+       tristate
+       default y if SCSI=n || SCSI=y
+       default m if SCSI=m
+
 config RAID_ATTRS
 	tristate "RAID Transport Class"
 	default n
 	depends on BLOCK
+	depends on SCSI_MOD
 	---help---
 	  Provides RAID
 

drivers/scsi/raid_class.c

···
 	 * emulated RAID devices, so start with SCSI */
 	struct raid_internal *i = ac_to_raid_internal(cont);
 
+#if defined(CONFIG_SCSI) || defined(CONFIG_SCSI_MODULE)
 	if (scsi_is_sdev_device(dev)) {
 		struct scsi_device *sdev = to_scsi_device(dev);
 
···
 
 		return i->f->is_raid(dev);
 	}
+#endif
 	/* FIXME: look at other subsystems too */
 	return 0;
 }