This patch adds dualhead support for lynx chips to the siliconmotion driver. 
It's semi-nonstandard due to the strange and limited nature of the lynx
architecture.  To enable dualhead add the following option to the device section
of your xorg.conf:
Option "Dualhead" "TRUE"

Limitations of the architecture:
- dualhead modes are limited to the same size and timing on both crtcs
- mode must be the same size as the panel
- LCD crtc is fixed at offset 0
- both crtc buffers must be within the range of the drawing engine
- drawing engine pitch must be wide enough for both crtcs