staging: r8188eu: Remove unnecessary list_head entry from recv_frame union

Struct recv_frame_hdr already contains a list head. This one is pointless.

Suggested-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>