st/xorg: Fix debug option function call typo.

src/gallium/state_trackers/xorg/xorg_driver.c

@@ -558,7 +558,7 @@ ScreenInit(int scrnIndex, ScreenPtr pScreen, int argc, char **argv)
     xf86SetBlackWhitePixels(pScreen);
 
     ms->exa = xorg_exa_init(pScrn);
-    ms->debug_fallback = debug_get_option_bool("XORG_DEBUG_FALLBACK", TRUE);
+    ms->debug_fallback = debug_get_bool_option("XORG_DEBUG_FALLBACK", TRUE);
 
     miInitializeBackingStore(pScreen);
     xf86SetBackingStore(pScreen);