python/regress: Clean up driver clear() interface.

src/gallium/state_trackers/python/tests/regress/fragment-shader/fragment-shader.py

@@ -122,7 +122,12 @@ def test(dev, name):
     fb.nr_cbufs = 1
     fb.set_cbuf(0, cbuf)
     ctx.set_framebuffer(fb)
-    ctx.surface_clear(cbuf, 0x80808080)
+    rgba = FloatArray(4);
+    rgba[0] = 0.5
+    rgba[1] = 0.5
+    rgba[2] = 0.5
+    rgba[3] = 0.5
+    ctx.clear(PIPE_CLEAR_COLOR, rgba, 0.0, 0)
 
     # vertex shader
     vs = Shader('''