drm/i915/bw: Extract platform-specific parameters

We got confirmation from the hardware team that the bandwidth parameters
deprogbwlimit and derating are platform-specific and not tied to the
display IP.  As such, let's make sure that we use platform checks for
those.

The rest of the members of struct intel_sa_info are tied to the display
IP and we will deal with them as a follow-up.

v2:
  - Use good old if-ladder instead of weird-looking pattern "assign ret,
    check platform, then return ret". (Jani, Matt)
  - Have a single call site for get_platform_bw_params() and pass the
    result as parameter to the *_get_bw_info() functions. (Jani)
  - Avoid using "plat" as abbreviation for "platform". (Jani)
  - s/_plat_bw_params/_bw_params/, since all of the instances are
    prefixed with platform names. (Jani)
  - s/struct intel_platform_bw_params/struct intel_soc_bw_params/.
    (Matt)
  - Do not return a default value; prefer to return NULL and
    intentionally cause a NULL pointer dereference if a platform is
    missing. (Gustavo)

v3:
  - Call get_soc_bw_params() only after the check on
    HAS_DISPLAY(display). (Jani)
  - Combine if-ladder branches for adl_s_bw_params into a single one.
    (Matt)
  - Flatten if-ladder by checking for WCL before PTL (as opposed to
    checking for WCL inside the brace for PTL). (Matt)
  - Bail out of intel_bw_init_hw() if display version is below 11.
    (Gustavo)

v4:
  - Drop drm_WARN() when no platform was matched to avoid
    special-casing DG2 and any other platform that doesn't use
    SoC-specific parameters. (Jani)
  - Pass dram_info to get_soc_bw_params() to keep a single call to
    intel_dram_info(). (Jani)
  - Don't use 2 separate if-ladders (one for client and another for
    discrete platforms) and keep a single one for simplicity. (Gustavo)

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20260518-separate-platform-from-diplay-ip-specific-bw-params-v4-2-918528006549@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>

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