[SCSI] ibmvscsi compatibility fix

Linda Xie ever so gently pointed out that she had a patch
to preserve compatibility with older SLES targets, and I told
her we didn't need to push it to mainline.

This patch explicitly checks the version of the IBMVSCSI target
and ensures that large scatterlists are not sent to older
targets.

Signed-off-by: Linda Xie <lxie@us.ibm.com>
Signed-off-by: Dave Boutcher <boutcher@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>