smb3: mark compression as CONFIG_EXPERIMENTAL and fix missing compression operation

Move SMB3.1.1 compression code into experimental config option,
and fix the compress mount option. Implement unchained LZ77
"plain" compression algorithm as per MS-XCA specification
section "2.3 Plain LZ77 Compression Algorithm Details".

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>