drm/nouveau: fix dma syncing for loops (v2)

The index variable should only be increased in one place.

Noticed this while trying to track down another oops.

v2: use while loop.

Fixes: f295c8cf ("drm/nouveau: fix dma syncing warning with debugging on.")
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210311043527.5376-1-airlied@gmail.com

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -556,7 +556,8 @@ nouveau_bo_sync_for_device(struct nouveau_bo *nvbo)
 	if (nvbo->force_coherent)
 		return;
 
-	for (i = 0; i < ttm_dma->num_pages; ++i) {
+	i = 0;
+	while (i < ttm_dma->num_pages) {
 		struct page *p = ttm_dma->pages[i];
 		size_t num_pages = 1;
 
@@ -587,7 +588,8 @@ nouveau_bo_sync_for_cpu(struct nouveau_bo *nvbo)
 	if (nvbo->force_coherent)
 		return;
 
-	for (i = 0; i < ttm_dma->num_pages; ++i) {
+	i = 0;
+	while (i < ttm_dma->num_pages) {
 		struct page *p = ttm_dma->pages[i];
 		size_t num_pages = 1;