LU-15197 llite: Do not count tiny write twice

LU-15197 llite: Do not count tiny write twice

We accidentally count bytes written with tiny write twice
in stats.  Remove the extra count.

This also has the positive effect of improving tiny write
performance by about 4% by removing an extra call to the
stats code (the main cost is ktime_get()).

Before, 8 byte dd:
13.9 MiB/s
After:
14.3 MiB/s

Test-parameters: trivial

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ia11e7f16e3e3d0c4012f87cde817ad7b21128fa8
Reviewed-on: https://review.whamcloud.com/45476
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Aurelien Degremont <degremoa@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>