Allow setting modes larger then panel for secondary output.
Allow setting modes larger then panel for secondary output.

  Sample usage on sm502:
$ DISPLAY=:0 xrandr --output VGA --newmode 1280x1024 109.00 1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
$ DISPLAY=:0 xrandr --addmode VGA 1280x1024
$ DISPLAY=:0 xrandr --output VGA --mode 1280x1024 --pos 768x176
  Last command assuming using XAA (with ``Virtual 2048 1024''), so that it
will have panel in top-left, and crt in bottom-right.

lumag/xf86-video-siliconmotion,lumag/xf86-video-siliconmotion