drm/{i915,xe}: convert i915 and xe display members into pointers

drm/{i915,xe}: convert i915 and xe display members into pointers

As the first step towards making struct intel_display an opaque pointer
in i915 and xe drivers, convert the struct drm_i915_private and struct
xe_device display members into pointers.

Initially, add temporary struct intel_display __display members, and
point display at it to avoid dynamic allocation. In the future, we can
drop this, and switch to dynamic allocation.

The conversion is done simply with sed:

sed -i 's/&\([a-zA-Z0-9_>.-]*\)\(dev_priv\|i915\|xe\)->display\([^.]\)/\1\2->display\3/g' \
    $(git ls-files -- drivers/gpu/drm/i915 drivers/gpu/drm/xe)

sed -i 's/\(dev_priv\|i915\|xe\)->display\./\1->display->/g' \
    $(git ls-files -- drivers/gpu/drm/i915 drivers/gpu/drm/xe)

With a couple of manual tweaks on top.

v2: Initialize i915->display also in selftest mock_gem_device()

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://lore.kernel.org/r/20250507152254.2398934-1-jani.nikula@intel.com