[SCSI] modalias for scsi devices

[SCSI] modalias for scsi devices

The following patch adds support for sysfs/uevent modalias
attribute for scsi devices (like disks, tapes, cdroms etc),
based on whatever current sd.c, sr.c, st.c and osst.c drivers
supports.

The modalias format is like this:

 scsi:type-0x04

(for TYPE_WORM, handled by sr.c now).

Several comments.

o This hexadecimal type value is because all TYPE_XXX constants
  in include/scsi/scsi.h are given in hex, but __stringify() will
  not convert them to decimal (so it will NOT be scsi:type-4).
  Since it does not really matter in which format it is, while
  both modalias in module and modalias attribute match each other,
  I descided to go for that 0x%02x format (and added a comment in
  include/scsi/scsi.h to keep them that way), instead of changing
  them all to decimal.

o There was no .uevent routine for SCSI bus.  It might be a good
  idea to add some more ueven environment variables in there.

o osst.c driver handles tapes too, like st.c, but only SOME tapes.
  With this setup, hotplug scripts (or whatever is used by the
  user) will try to load both st and osst modules for all SCSI
  tapes found, because both modules have scsi:type-0x01 alias).
  It is not harmful, but one extra module is no good either.
  It is possible to solve this, by exporting more info in
  modalias attribute, including vendor and device identification
  strings, so that modalias becomes something like
    scsi:type-0x12:vendor-Adaptec LTD:device-OnStream Tape Drive
  and having that, match for all 3 attributes, not only device
  type.  But oh well, vendor and device strings may be large,
  and they do contain spaces and whatnot.
  So I left them for now, awaiting for comments first.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>