cifs: Remove symlink member from cifs_open_info_data union

Member 'symlink' is part of the union in struct cifs_open_info_data. Its
value is assigned on few places, but is always read through another union
member 'reparse_point'. So to make code more readable, always use only
'reparse_point' member and drop whole union structure. No function change.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>