drm/i915/gsc: define gsc fw

Add FW definition and the matching override modparam.

The GSC FW has both a release version, based on platform and a rolling
counter, and a compatibility version, which is the one tracking
interface changes. Since what we care about is the interface, we use
the compatibility version in the binary names.

Same as with the GuC, a major version bump indicate a
backward-incompatible change, while a minor version bump indicates a
backward-compatible one, so we use only the former in the file name.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230825162754.1949838-1-daniele.ceraolospurio@intel.com