ice: implement CPI support for E825C

Add full CPI (Converged PHY Interface) command handling required for
E825C devices. The CPI interface allows the driver to interact with
PHY-side control logic through the LM/PHY command registers, including
enabling/disabling/selection of PHY reference clock.

This patch introduces:
 - a new CPI subsystem (ice_cpi.c / ice_cpi.h) implementing the CPI
   request/acknowledge state machine, including REQ/ACK protocol,
   command execution, and response handling
 - helper functions for reading/writing PHY registers over Sideband
   Queue
 - CPI command execution API (ice_cpi_exec) and a helper for enabling or
   disabling Tx reference clocks (CPI 0xF1 opcode 'Config PHY clocking')
 - assurance of CPI transaction serialization into the CPI core.
   CPI REQ/ACK is a multi-step handshake    and must be executed
   atomically per PHY. Centralize the lock in ice_cpi_exec() and
   use adapter-scoped per-PHY mutexes, which match the hardware sharing
   model across PFs.
 - addition of the non-posted write opcode (wr_np) to SBQ
 - Makefile integration to build CPI support together with the PTP stack

This provides the infrastructure necessary to support PHY-side
configuration flows on E825C and is required for advanced link control
and Tx reference clock management.

Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Grzegorz Nitka <grzegorz.nitka@intel.com>
Link: https://patch.msgid.link/20260607183045.1213735-12-grzegorz.nitka@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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