lightnvm: sectors first in ppa list

The Westlake controller requires that the PPA list has sectors defined
sequentially. Currently, the PPA list is created with planes first, then
sectors. Change this to sectors first, then planes.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>