Revert "filesetup: honor the offset option"

Revert "filesetup: honor the offset option"

This reverts commit ad46c5715ffc5d4e70d2e941225b1f504f23e409.

The commit tried to fix a failure observed with --offset=90%, --size=1T
and --ioengine=null options. However, it affected fio behavior not only
for null ioengine but also for other all ioengines. It changed io_size,
then I/O read or written bytes are not same as that specified with
command line 'size' option. This caused t/zbd/test-zbd-support test
script failures for zoned block devices: test cases #17, #28 and #38
failed.

To prepare for other fix with limited ioengine impacts, revert the fix
which affects all ioengines.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>