[writeboost] Reverse the order of stat flag

Doing this makes the statistic more readable and easy to format.
(See the stat example below)

Also, This fix is required to get consistent with Documentation and
status class in dmts.

Example:
write? hit? on_buffer? fullsize? count
0 0 0 0 8
0 0 0 1 9
0 0 1 0 10
0 0 1 1 11
0 1 0 0 12
0 1 0 1 13
0 1 1 0 14
0 1 1 1 15
1 0 0 0 16
1 0 0 1 17
1 0 1 0 18
1 0 1 1 19
1 1 0 0 20
1 1 0 1 21
1 1 1 0 22
1 1 1 1 23

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
Merge pull request #14 from akiradeveloper/feature/reverse-stat

Feature/reverse stat