phy: lynx-28g: refactor lane->interface to lane->mode

phy: lynx-28g: refactor lane->interface to lane->mode

Lynx 28G is a multi-protocol SerDes - it handles serial Ethernet, PCIe,
SATA.

The driver should not use the phylib-specific phy_interface_t as an
internal data representation, but something specific to its internal
capabilities, and only convert to phy_interface_t when PHY_MODE_ETHERNET
is selected and used.

Otherwise it has no way of representing the non-Ethernet lanes (which
was not a short-term goal when the driver was introduced, and is not a
goal per se right now either, but should nonetheless be possible).

Prefer the "enum lynx_lane_mode" name over "lynx_28g_lane_mode", in
preparation of future Lynx 10G SerDes support. This SerDes is part of
the same IP family and has similar capabilities, and will reuse some
code, hence the common data type.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20251125114847.804961-12-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>