phy: lynx-28g: provide default lynx_lane_supports_mode() implementation

phy: lynx-28g: provide default lynx_lane_supports_mode() implementation

For the 28G Lynx, there are situations where a protocol is not supported
on a lane despite there being a PCCR register and protocol converter
available:
- LX2160A SerDes 1: reference manual documents PCCD fields E25GC_CFG and
  E25GD_CFG and protocol converter registers E25GCCR1..E25GCCR3 /
  E25GDCR1..E25GDCR3, but nonetheless, Table 289. SerDes 1 protocol
  mapping shows no RCW[SRDS_PRTCL_S1] value for which lanes C and D
  support 25G
- when using the "fsl,lynx-28g" fallback compatible string, we don't
  want to offer 25GbE because we don't know if the lane supports it,
  even though we know how to reach the PCCR and protocol converter
  registers for it.

But for the upcoming 10G Lynx SerDes, the above situations don't exist.
There, if we know how to reach the PCCR and protocol converter
registers on a lane, we implicitly know that the protocol is supported
there, so implementing priv->info->lane_supports_mode() would be
redundant.

Implement lynx_lane_supports_mode_default() which decides whether a lane
mode is supported just based on priv->info->get_pccr() and
priv->info->get_pcvt_offset().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20260610151952.2141019-8-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>