drm/i915: Apply WaUse32BppForSRWM to elk as well as ctg

The w/a database lists this for both ctg and elk. So let's apply it to
elk as well. And add the w/a name.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210514125751.17075-5-ville.syrjala@linux.intel.com


Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>