cifs: remove uneeded __KERNEL__ block from cifsacl.h

...and make those symbols static in cifsacl.c. Nothing outside
of that file refers to them.

Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>