drm/i915: Convert INTEL_INFO()->display to a pointer

Rather than embeddeding the display's device info within the main device
info structure, just provide a pointer to the display-specific
structure.  This is in preparation for moving the display device info
definitions into the display code itself and for eventually allowing the
pointer to be assigned at runtime on platforms that use GMD_ID for
device identification.

In the future, this will also eventually allow the same display device
info structures to be used outside the current i915 code (e.g., from the
Xe driver).

v2:
 - Move introduction of DISPLAY_INFO() to this patch.  (Andrzej)
v3:
 - Also use DISPLAY_INFO() in intel_display_reg_defs.h.  (Andrzej)
 - Use "{}" instead of "{ 0 }" for empty struct init.  (Jani)

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230523195609.73627-3-matthew.d.roper@intel.com