when probing a device the midlayer queries its inquiry data and

when probing a device the midlayer queries its inquiry data and
keeps it on the stack till we attach a driver to it. then it copies
the inquiry data int the scsi_link struct.

this diff uses the scsi_link struct instead of the stack for that data,
which makes the inq data for users of the scsi_link struct available much
earlier during device probe.

review and feedback from both krw@ and marco@