lightnvm: fix memory leak when submit fails

The allocated page is not released if error occurs in
nvm_submit_io_sync_raw(). __free_page() is moved ealier to avoid
possible memory leak issue.

Fixes: aff3fb18

 ("lightnvm: move bad block and chunk state logic to core")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>