[PATCH] SCSI tape log message fixes

This patch changes the st console/log messages:

- __GFP_NOWARN added to buffer allocation to suppress useless messages
  when having to use smaller than default segments
- move log message from enlarge_buffer() to caller so that the tape name
  can be printed and remove some debugging messages; now the st messages
  should include drive name where applicable (a problem reported by
  Hironobu Ishii)
- setting options is logged only when debugging; the most important
  options are now seen in sysfs