Clean up unit prefixes for binary multiples in comments and prints

Clean up unit prefixes for binary multiples in comments and prints

Change comments and prints that are referring to values based on
binary multiples to use IEC 80000-13 prefixes for binary
multiples rather than SI prefixes for decimal multiples (e.g.,
KiB, MiB, and GiB rather than KB, MB, and GB).

Includes a fix for the rate_min print that was printing "KB/s"
although it was really printing bytes per second.

Includes a fix for goptions confusing the PB and TB units (while
changing them to PiB and TiB).

Signed-off-by: Jens Axboe <axboe@fb.com>