drm/ttm: Fix 'buf' pointer update in ttm_bo_vm_access_kmap() (v2)

The buf pointer was not being incremented inside the loop
meaning the same block of data would be read or written
repeatedly.

(v2) Change 'buf' pointer to uint8_t* type

Cc: stable@vger.kernel.org
Fixes: 09ac4fcb ("drm/ttm: Implement vm_operations_struct.access v2")
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -316,7 +316,7 @@ static void ttm_bo_vm_close(struct vm_area_struct *vma)
 
 static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
 				 unsigned long offset,
-				 void *buf, int len, int write)
+				 uint8_t *buf, int len, int write)
 {
 	unsigned long page = offset >> PAGE_SHIFT;
 	unsigned long bytes_left = len;
@@ -345,6 +345,7 @@ static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
 		ttm_bo_kunmap(&map);
 
 		page++;
+		buf += bytes;
 		bytes_left -= bytes;
 		offset = 0;
 	} while (bytes_left);