drm/xe/display: Fix fbdev GGTT mapping handling.

drm/xe/display: Fix fbdev GGTT mapping handling.

FBDEV ggtt is not restored correctly, add missing GGTT flag to
intel_fbdev_fb_alloc to make it work. This ensures that the global
GGTT mapping is always restored on resume. The GGTT mapping would
otherwise be created in intel_fb_pin_to_ggtt() by intel_fbdev anyway.

This fixes the fbdev device not working after resume.

Fixes: 67a98f7e27ba ("drm/xe/display: Re-use display vmas when possible")
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250305110106.564366-1-dev@lankhorst.se
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>