[drm] fix radeon aperture issue

Ben noticed that on certain cards we've landed the AGP space on top of
the second aperture instead of after it..  Which messes things up a lot
on those machines.

This just moves the gart further out, a more correct fix is in the works
from Ben for after 2.6.15.

Signed-off-by: Dave Airlie <airlied@linux.ie>
CC: Ben Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/drm/radeon_cp.c

@@ -1522,7 +1522,7 @@ static int radeon_do_init_cp(drm_device_t * dev, drm_radeon_init_t * init)
 
 	dev_priv->gart_size = init->gart_size;
 	dev_priv->gart_vm_start = dev_priv->fb_location
-	    + RADEON_READ(RADEON_CONFIG_APER_SIZE);
+	    + RADEON_READ(RADEON_CONFIG_APER_SIZE) * 2;
 
 #if __OS_HAS_AGP
 	if (!dev_priv->is_pci)