[PATCH] fix disk->id abuse

[Robert Millan]

disk->id is supposed to be filled with a per-disk value so that the disk
cache manager can identify individual disks.

For single-disk drivers, a constant is enough.  But it seems someone started
using pointers to strings for them, and then we all (including me) copied.

Then I see disk/scsi.c doing the same thing, but this time it's a real problem
since it's not a single-disk driver.

So this patch means to solve both issues;  makes single-disk drivers use a
constant directly (since a pointer to string is meaningless and confusing),
and disk/scsi.c use LUNs which (I believe) will work as unique identifiers.

Marco, could you confirm this is ok (specially the latter)?

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."

disk_id_abuse.diff
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