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There was a misunderstanding in how firmware file compatibility should
be managed within i915. This has been clarified as:
  i915 must support all existing firmware releases forever
  new minor firmware releases should replace prior versions
  only backwards compatibility breaking releases should be a new file

This patch cleans up the single fallback file support that was added
as a quick fix emergency effort. That is now removed in preference to
supporting arbitrary numbers of firmware files per platform.

The patch also adds support for having GuC firmware files that are
named by major version only (because the major version indicates
backwards breaking changes that affect the KMD) and for having HuC
firmware files with no version number at all (because the KMD has no
interface requirements with the HuC).

For GuC, the driver will report via dmesg if the found file is older than
expected. For HuC, the KMD will no longer require updating for any new
HuC release so will not be able to report what the latest expected
version is.
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220906230147.479945-1-daniele.ceraolospurio@intel.com