Disable spread spectrum clock usage.

The spread spectrum clock generator that improves EMI characteristics for
laptop screens lives in an external chip that is programmed over an i2c bus.
Without correct programming, attempts to use this mode for the LVDS can
result in a DC signal being sent to the panel.

Until we find programming information for this external chip, we should
leave this mode disabled.

src/i830_display.c

@@ -476,8 +476,10 @@ i830PipeSetMode(ScrnInfoPtr pScrn, DisplayModePtr pMode, int pipe)
 
     if (outputs & (PIPE_TV_ACTIVE | PIPE_TV2_ACTIVE))
 	dpll |= PLL_REF_INPUT_TVCLKINBC;
+#if 0    
     else if (outputs & (PIPE_LCD_ACTIVE))
 	dpll |= PLLB_REF_INPUT_SPREADSPECTRUMIN;
+#endif
     else	
 	dpll |= PLL_REF_INPUT_DREFCLK;