hyperv/storvsc: Claim SPC-3 conformance, thus enable UNMAP support

The Hyper-V on pre-win10 systems will only report SPC-2 conformance,
but it actually conforms to SPC-3. The INQUIRY response is adjusted
to propagate the SPC-3 version information to CAM.

Submitted by: Hongjiang Zhang <honzhan microsoft com>
MFC after: 3 days
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D7405