drm/xe: Fix platform order

drm/xe: Fix platform order

Platform order in enum xe_platform started to be used by some parts of
the code, like the GuC/HuC firmware loading logic. The order itself is
not very important, but it's better to follow a convention: as was
documented in the comment above the enum, reorder the platforms by
graphics version. While at it, remove the gen terminology.

v2:
  - Use "graphics version" instead of chronological order (Matt Roper)
  - Also change pciidlist to follow the same order
  - Remove "gen" from comments around enum xe_platform

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230331230902.1603294-1-lucas.demarchi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>