'cable_test_tdr_req_info' is unused since the original
commit f2bc8ad3 ("net: ethtool: Allow PHY cable test TDR data to
configured").

Remove it.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>