drm/nouveau: fix vram page mapping when crossing page table boundaries

Hopefully the cause of nvc0 "page jumping" issue.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_vm.c b/drivers/gpu/drm/nouveau/nouveau_vm.c
index 0059e6f..519a6b4 100644
--- a/drivers/gpu/drm/nouveau/nouveau_vm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_vm.c
@@ -58,6 +58,7 @@
 			num -= len;
 			pte += len;
 			if (unlikely(end >= max)) {
+				phys += len << (bits + 12);
 				pde++;
 				pte = 0;
 			}