In the old days, sbp2 used to coerce all MODE SENSE commands into the
10 bytes version.  When all command set conversions were removed from
sbp2 several months ago, sdev->use_10_for_ms = 1 was added.  Meaning,
higher SCSI layers preferred the 10 bytes version but would try the 6
bytes version if the former failed.

Recently, a problem with the 10 bytes version was discovered.  An Initio
INIC-1530 firmware accepted the 10 bytes version but replied with bogus
data, showing the HDD incorrectly as write-protected.  Since RBC
actually mandates MODE SENSE (6), I checked which version was sent by
Windows XP and Mac OS X 10.3 to an SBP-2 target hosted by Linux --- it
was the 6 bytes version.  (Exception: OS X sent the 10 bytes version to
an MMC target.  RBC and SBC got MODE SENSE (6).)

Therefore, drop the use_10_for_ms flag from sbp2.  Now the upper layers
will try MODE SENSE (6) before MODE SENSE (10) on all SBP-2 devices.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>