drm/modeset: Handle tiled displays in pan_display_atomic.

drm/modeset: Handle tiled displays in pan_display_atomic.

commit f4a9dd57e549a17a7dac1c1defec26abd7e5c2d4 upstream.

Tiled displays have a different x/y offset to begin with. Instead of
attempting to remember this, just apply a delta instead.

This fixes the first tile being duplicated on other tiles when vt
switching.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20250116142825.3933-1-dev@lankhorst.se
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>