SCSI: Fix problems with non-power-of-two sector size discs

SCSI: Fix problems with non-power-of-two sector size discs

We can't support them, but the system should disable them cleanly
and continue when they're detected (at the moment it
dumps a stack trace).

The fix (hack) is to set them to zero size and 512 byte
sectors.  This means they're still amenable to ioctls (like
to reformat them with a useful block size) but cannot
be read from or written to.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>