btrfs: un-deprecate ioctls START_SYNC and WAIT_SYNC

The two ioctls START_SYNC and WAIT_SYNC were mistakenly marked as
deprecated and scheduled for removal but we actualy do use them for
'btrfs subvolume delete -C/-c'. The deprecated thing in ebc87351
should have been just the async flag for subvolume creation.

The deprecation has been added in this development cycle, remove it
until it's time.

Fixes: ebc87351 ("btrfs: Deprecate BTRFS_SUBVOL_CREATE_ASYNC flag")
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -4195,9 +4195,6 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
 	u64 transid;
 	int ret;
 
-	btrfs_warn(root->fs_info,
-	"START_SYNC ioctl is deprecated and will be removed in kernel 5.7");
-
 	trans = btrfs_attach_transaction_barrier(root);
 	if (IS_ERR(trans)) {
 		if (PTR_ERR(trans) != -ENOENT)
@@ -4225,9 +4222,6 @@ static noinline long btrfs_ioctl_wait_sync(struct btrfs_fs_info *fs_info,
 {
 	u64 transid;
 
-	btrfs_warn(fs_info,
-		"WAIT_SYNC ioctl is deprecated and will be removed in kernel 5.7");
-
 	if (argp) {
 		if (copy_from_user(&transid, argp, sizeof(transid)))
 			return -EFAULT;