This patch makes sure CRTC2_OFFSET_CNTL is cleared. None of the options in
this register should be enabled with our current driver, and some firmwares
setup a tiled display, which we _must_ disable for now. Without this, the
second screen is completely scrambled on some PowerMacs.

Index: xc/programs/Xserver/hw/xfree86/drivers/ati/radeon_driver.c
===================================================================
--- xc.orig/programs/Xserver/hw/xfree86/drivers/ati/radeon_driver.c     2004-12-05 17:11:57.704394872 +1100
+++ xc/programs/Xserver/hw/xfree86/drivers/ati/radeon_driver.c  2004-12-05 17:13:38.156123888 +1100
@@ -6605,8 +6605,13 @@
                                     ? RADEON_CRTC2_V_SYNC_POL
                                     : 0));

+    /* We must make sure Tiling is disabled. It seem all other fancy
+     * options in there can be safely disabled too
+     */
    save->crtc2_offset      = 0;
-    save->crtc2_offset_cntl = INREG(RADEON_CRTC2_OFFSET_CNTL);
+    save->crtc2_offset_cntl = 0;
+
+
    /* this should be right */
    if (info->MergedFB) {
    save->crtc2_pitch  = (((info->CRT2pScrn->displayWidth * pScrn->bitsPerPixel) +