drm/i915/dg2: Recognize pre-production hardware

The first production SoC steppings for DG2 were C0 (for G10), B1 (for
G11), and A1 (for G12).  This corresponds to PCI revision IDs 0x8, 0x5,
and 0x1 respectively.  Add this information to the driver's
pre-production detection.

Bspec: 44477
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230816214201.534095-8-matthew.d.roper@intel.com