drm/i915/dg2: Introduce Wa_18018764978

Wa_18018764978 applies to specific steppings of DG2 (G10 C0+,
G11 and G12 A0+). Clean up style in function at the same time.

Bspec: 66622

Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221123183648.407058-1-matthew.s.atwood@intel.com


(cherry picked from commit 468a4e63)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>