fs: add a set_acl inode operation

This will allow moving all the Posix ACL handling into the VFS and clean
up tons of cruft in the filesystems.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/fs.h

@@ -1580,6 +1580,7 @@ struct inode_operations {
 			   struct file *, unsigned open_flag,
 			   umode_t create_mode, int *opened);
 	int (*tmpfile) (struct inode *, struct dentry *, umode_t);
+	int (*set_acl)(struct inode *, struct posix_acl *, int);
 } ____cacheline_aligned;
 
 ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,