drm/vmwgfx: Trigger a modeset when the screen moves

When multi-monitor is cycled the X,Y position of the Screen Target will
likely change but the resolution will not. We need to trigger a modeset
when this occurs in order to recreate the Screen Target with the correct
X,Y position.

Fixes a bug where multiple displays are shown in a single scrollable
host window rather than in 2+ windows on separate host displays.

Fixes: 42682693

 ("drm/vmwgfx: Filter modes which exceed graphics memory")
Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240624205951.23343-1-ian.forbes@broadcom.com