net: phy: microchip_t1s: add SQI support for LAN867x Rev.D0 PHYs

net: phy: microchip_t1s: add SQI support for LAN867x Rev.D0 PHYs

Add support for Signal Quality Index (SQI) reporting in the
Microchip T1S PHY driver for LAN867x Rev.D0 (OATC14-compliant) PHYs.

This patch registers the following callbacks in the microchip_t1s driver
structure:

- .get_sqi      - returns the current SQI value
- .get_sqi_max  - returns the maximum SQI value

This enables ethtool to report the SQI value for LAN867x Rev.D0 PHYs.

Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251201032346.6699-3-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>