libata-scsi: correct SPC version descriptor

The comment suggests we should be having an SPC-3 version descriptor
but the 0260h is the code for "SPC-2 (no version claimed)". Correct
it to 0300h so that it has the "SPC-3 (no version claimed)" descriptor.

Note that we are claiming SPC-3 version compatibility in the VERSION
field of the standard INQUIRY data. Therefore, I assume the typo was
on the code but not on the comment.

Signed-off-by: Tom Yan <tom.ty89@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>