drm/i915/display: Extract display init from intel_device_info_runtime_init

Moving display-specific runtime info initialization into display/ makes
the display code more self-contained and also makes it easier to call
from the Xe driver.

v2:
 - Drop unnecessary display/ prefix from #includes.  (Jani)
 - Clear runtime info if fusing leaves no pipes remaining, the same as
   we do when fusing indicates the entire display controller is
   unavailable.  (Jani)
 - Move adjustment of DRIVER_MODESET / DRIVER_ATOMIC after call to
   intel_display_device_info_runtime_init(); HAS_DISPLAY may have
   changed to false during the runtime init.  (Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230602181450.1151368-1-matthew.d.roper@intel.com