dm: Make use of __assign_bit() API

We have for some time the __assign_bit() API to replace
open coded
    if (foo)
        __set_bit(n, bar);
    else
        __clear_bit(n, bar);

Use this API to simplify the code. No functional change
intended.
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

drivers/md/dm-clone-metadata.c

@@ -530,10 +530,7 @@ static int __load_bitset_in_core(struct dm_clone_metadata *cmd)
 		return r;
 
 	for (i = 0; ; i++) {
-		if (dm_bitset_cursor_get_value(&c))
-			__set_bit(i, cmd->region_map);
-		else
-			__clear_bit(i, cmd->region_map);
+		__assign_bit(i, cmd->region_map, dm_bitset_cursor_get_value(&c));
 
 		if (i >= (cmd->nr_regions - 1))
 			break;