drm/i915/dg1: Apply WA 1409120013 and 14011059788

DG1 is missing those two WA so instead of copy and paste it to the DG1
function, here calling the function that implements it.

While at it also renaming tgl_init_clock_gating to
gen12lp_init_clock_gating as it is also used by DG1, RKL and ADL-S.

Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210113133759.72055-1-jose.souza@intel.com