target: Return correct ASC for unimplemented VPD pages

commit bb1acb2ee038a6c13ee99e0b9fb44dacb4a9de84 upstream.

My draft of SPC-4 says:

    If the device server does not implement the requested vital product
    data page, then the command shall be terminated with CHECK CONDITION
    status, with the sense key set to ILLEGAL REQUEST, and the
    additional sense code set to INVALID FIELD IN CDB.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>