drm/xe/fb: Use the correct gtt view for remapped FBs

drm/xe/fb: Use the correct gtt view for remapped FBs

Use the proper gtt view from the plane state rather than always
assuming that it came directly from the FB. This is in the DPT
codepath so the view should currently always come from the FB,
but in the future we may also want per-plane remapping with DPT.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260416174448.28264-2-ville.syrjala@linux.intel.com