net: phy: microchip_t1s: add c45 direct access in LAN865x internal PHY

net: phy: microchip_t1s: add c45 direct access in LAN865x internal PHY

This patch adds c45 registers direct access support in Microchip's
LAN865x internal PHY.

OPEN Alliance 10BASE-T1x compliance MAC-PHYs will have both C22 and C45
registers space. If the PHY is discovered via C22 bus protocol it assumes
it uses C22 protocol and always uses C22 registers indirect access to
access C45 registers. This is because, we don't have a clean separation
between C22/C45 register space and C22/C45 MDIO bus protocols. Resulting,
PHY C45 registers direct access can't be used which can save multiple SPI
bus access. To support this feature, set .read_mmd/.write_mmd in the PHY
driver to call .read_c45/.write_c45 in the OPEN Alliance framework
drivers/net/ethernet/oa_tc6.c

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
Link: https://patch.msgid.link/20240909082514.262942-8-Parthiban.Veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>