drm/i915/dg1: Add initial DG1 workarounds

DG1 shares some workarounds with TGL and RKL and also has some
additional workarounds of its own.

v2: Correct location of Wa_1408615072 (JohnH).
v3: Apply WAs 1606700617, 18011464164 and 22010931296 to DG1 (José)
v4 (Anusha)
  - Add Wa_22010271021
  - s/Wa_14010096844/Wa_1409836686
v5:
  - Extend Wa_14010919138 to all revs (Matt Atwood)
  - Power gate media is global gen12 design. (Rodrigo)
  - Rebase (Lucas)
v6: use REG_BIT() to fix checkpatch warning (Lucas)

BSpec: 53508

Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201014191937.1266226-8-lucas.demarchi@intel.com