lib/intel_batchbuffer: igt_ namespace for the buffer structure

Step one to properly namespace the rendercpy/mediafill functions. Als
give the buf_height/width helpers a proper igt_ prefix.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/tests/gem_render_tiled_blits.c b/tests/gem_render_tiled_blits.c
index 71dfdd6..0552af1 100644
--- a/tests/gem_render_tiled_blits.c
+++ b/tests/gem_render_tiled_blits.c
@@ -84,7 +84,7 @@
 	drm_intel_bufmgr *bufmgr;
 	struct intel_batchbuffer *batch;
 	uint32_t *start_val;
-	struct scratch_buf *buf;
+	struct igt_buf *buf;
 	uint32_t start = 0;
 	int i, j, fd, count;