drm/nv10: Change the BO size threshold determining the memory placement range.

Fixes the framebuffer memory allocation failure seen on some
low-memory cards, followed by X refusing to start.

https://bugs.freedesktop.org/show_bug.cgi?id=42384Reported-by: NChris Paulson-Ellis <chris@edesix.com>
Signed-off-by: NFrancisco Jerez <currojerez@riseup.net>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -148,7 +148,7 @@ set_placement_range(struct nouveau_bo *nvbo, uint32_t type)
 
 	if (dev_priv->card_type == NV_10 &&
 	    nvbo->tile_mode && (type & TTM_PL_FLAG_VRAM) &&
-	    nvbo->bo.mem.num_pages < vram_pages / 2) {
+	    nvbo->bo.mem.num_pages < vram_pages / 4) {
 		/*
 		 * Make sure that the color and depth buffers are handled
 		 * by independent memory controller units. Up to a 9x