cifs: Remove {cifs,nfs}_fscache_release_page()

Remove {cifs,nfs}_fscache_release_page() from fs/cifs/fscache.h.  This
functionality got built directly into cifs_release_folio() and will
hopefully be replaced with netfs_release_folio() at some point.

The "nfs_" version is a copy and paste error and should've been altered to
read "cifs_".  That can also be removed.

Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Steve French <smfrench@gmail.com>
cc: linux-cifs@vger.kernel.org
cc: samba-technical@lists.samba.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>