[SCSI] stex: update device id info

- add comments for various devices
- remove unused device ids(0xf350, 0x4301, 0x8301, 0x8302)
- add new device id(0xe350)
- fix vendor id of st_vsc
- modify Kconfig help info

Signed-off-by: Ed Lin <ed.lin@promise.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>