fs: remove dead check

Above we call super_lock_excl() which waits until the superblock is
SB_BORN and since SB_BORN is never unset once set this check can never
fire. Plus, we also hold an active reference at this point already so
this superblock can't even be shutdown.

Link: https://lore.kernel.org/r/20231104-vfs-multi-device-freeze-v2-1-5b5b69626eac@kernel.orgTested-by: Chandan Babu R <chandanbabu@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/super.c

@@ -1996,11 +1996,6 @@ int freeze_super(struct super_block *sb, enum freeze_holder who)
 		goto retry;
 	}
 
-	if (!(sb->s_flags & SB_BORN)) {
-		super_unlock_excl(sb);
-		return 0;	/* sic - it's "nothing to do" */
-	}
-
 	if (sb_rdonly(sb)) {
 		/* Nothing to do really... */
 		sb->s_writers.freeze_holders |= who;