mtip32xx: Reduce the number of unaligned writes to 2

After several experiments, deduced the the optimal number of unaligned
writes to be 2. Changing the value accordingly.

Signed-off-by: Asai Thambi S P <asamymuthupa@micron.com>
Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
Signed-off-by: Jens Axboe <axboe@fb.com>