[SCSI] sg: do not set VM_IO flag on mmap-ed pages

Further to the problem discussed in this post:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112540053711489&w=2

It seems that the sg driver does not need to set the VM_IO flag
on pages that it memory maps to the user space since they are
not from the IO space. Ahmed Teirelbar <ahmed.teirelbar@adic.com>
wants the facility and has tested this patch as I have without
adverse effects.

The oops protection is still important. Some users really did
try and use dio transfers from the sg driver to memory mapped
IO space (on a video capture card if my memory serves) during the
lk 2.4 series. I'm not sure how successful it was but that will
now be politely refused in lk 2.6.13+ .

Changelog:
   - set the page flags for sg's reserved buffer mmap-ed
     to the user space to VM_RESERVED (rather than
     VM_RESERVED | VM_IO )

Signed-off-by: Douglas Gilbert <dougg@torque.net>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>