drm/i915/huc: differentiate the 2 steps of the MTL HuC auth flow

Before we add the second step of the MTL HuC auth (via GSC), we need to
have the ability to differentiate between them. To do so, the huc
authentication check is duplicated for GuC and GSC auth, with
GSC-enabled binaries being considered fully authenticated only after
the GSC auth step.

To report the difference between the 2 auth steps, a new case is added
to the HuC getparam. This way, the clear media driver can start
submitting before full auth, as partial auth is enough for those
workloads.

v2: fix authentication status check for DG2

v3: add a better comment at the top of the HuC file to explain the
    different approaches to load and auth (John)

v4: update call to intel_huc_is_authenticated in the pxp code to check
for GSC authentication

v5: drop references to meu and esclamation mark in huc_auth print (John)

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>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com> #v2
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230531235415.1467475-5-daniele.ceraolospurio@intel.com