net: phy: microchip_t1s:: add cable diagnostic support for LAN867x Rev.D0

net: phy: microchip_t1s:: add cable diagnostic support for LAN867x Rev.D0

Enable Open Alliance TC14 (OATC14) 10Base-T1S cable diagnostic feature
for Microchip LAN867x Rev.D0 PHY by implementing `cable_test_start` and
`cable_test_get_status` using the generic C45 functions. This allows the
`ethtool` utility to perform cable diagnostic tests directly on the PHY,
improving network troubleshooting and maintenance.

Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Link: https://patch.msgid.link/20251105051213.50443-3-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>