Allow setting per-file compression via SMB2/3

Allow cifs/smb2/smb3 to return whether or not a file is compressed
via lsattr, and allow SMB2/SMB3 to set the per-file compression
flag ("chattr +c filename" on an smb3 mount).

Windows users often set the compressed flag (it can be
done from the desktop and file manager).  David Disseldorp
has patches to Samba server to support this (at least on btrfs)
which are complementary to this

Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/smb2proto.h

@@ -142,6 +142,8 @@ extern int SMB2_set_eof(const unsigned int xid, struct cifs_tcon *tcon,
 extern int SMB2_set_info(const unsigned int xid, struct cifs_tcon *tcon,
 			 u64 persistent_fid, u64 volatile_fid,
 			 FILE_BASIC_INFO *buf);
+extern int SMB2_set_compression(const unsigned int xid, struct cifs_tcon *tcon,
+				u64 persistent_fid, u64 volatile_fid);
 extern int SMB2_oplock_break(const unsigned int xid, struct cifs_tcon *tcon,
 			     const u64 persistent_fid, const u64 volatile_fid,
 			     const __u8 oplock_level);