lightnvm: pblk: use exact free block counter in RL

Until now, pblk's rate-limiter has used a heuristic to reserve space for
GC I/O given that the over-provision area was fixed.

In preparation for allowing to define the over-provision area on target
creation, define a dedicated free_block counter in the rate-limiter to
track the number of blocks being used for user data.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
index 39a2e19..fd38036 100644
--- a/drivers/lightnvm/pblk-recovery.c
+++ b/drivers/lightnvm/pblk-recovery.c
@@ -989,10 +989,8 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 	}
 	spin_unlock(&l_mg->free_lock);
 
-	if (is_next) {
+	if (is_next)
 		pblk_line_erase(pblk, l_mg->data_next);
-		pblk_rl_free_lines_dec(&pblk->rl, l_mg->data_next);
-	}
 
 out:
 	if (found_lines != recovered_lines)