lightnvm: pblk: rename sync_point to flush_point

Sync point is a really confusing name for keeping track of
the last entry that needs to be flushed so change the name
to to flush_point instead.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-write.c

@@ -508,7 +508,7 @@ static int pblk_submit_write(struct pblk *pblk)
 	if (!secs_avail)
 		return 1;
 
-	secs_to_flush = pblk_rb_sync_point_count(&pblk->rwb);
+	secs_to_flush = pblk_rb_flush_point_count(&pblk->rwb);
 	if (!secs_to_flush && secs_avail < pblk->min_write_pgs)
 		return 1;