drm/nv50: make pushbuf dma object cover entire vm

This allows us to submit push buffers from any memtype to the hardware.
We'll need this ability for VRAM index buffers at some point.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.c b/drivers/gpu/drm/nouveau/nouveau_dma.c
index b9c80bb..679b03c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dma.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dma.c
@@ -182,12 +182,12 @@
 	      int delta, int dwords)
 {
 	struct nouveau_bo *pb = chan->pushbuf_bo;
-	uint64_t offset = (bo->bo.mem.mm_node->start << PAGE_SHIFT) + delta;
+	uint64_t offset = bo->bo.offset + delta;
 	int ip = (chan->dma.ib_put * 2) + chan->dma.ib_base;
 
 	BUG_ON(chan->dma.ib_free < 1);
-	nouveau_bo_wr32(pb, ip++, offset);
-	nouveau_bo_wr32(pb, ip++, dwords << 10);
+	nouveau_bo_wr32(pb, ip++, lower_32_bits(offset));
+	nouveau_bo_wr32(pb, ip++, upper_32_bits(offset) | dwords << 10);
 
 	chan->dma.ib_put = (chan->dma.ib_put + 1) & chan->dma.ib_max;
 	nvchan_wr32(chan, 0x8c, chan->dma.ib_put);