gallium/auxiliary/vl: Fix a couple of warnings

Remove unused functions and mark unhandled default case with
unreachable.

Signed-off-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/gallium/auxiliary/vl/vl_mpeg12_bitstream.c

@@ -617,12 +617,6 @@ DIV2DOWN(int todiv)
    return (todiv&~1)/2;
 }
 
-static inline int
-DIV2UP(int todiv)
-{
-   return (todiv+1)/2;
-}
-
 static inline void
 motion_vector(struct vl_mpg12_bs *bs, int r, int s, int dmv, short delta[2], short dmvector[2])
 {

src/gallium/auxiliary/vl/vl_mpeg12_decoder.c

@@ -388,8 +388,8 @@ MotionVectorToPipe(const struct pipe_mpeg12_macroblock *mb, unsigned vector,
          mv.bottom.weight = weight;
          break;
 
-      default: // TODO: Support DUALPRIME and 16x8
-         break;
+      default:
+         unreachable("TODO: Support DUALPRIME and 16x8");
       }
    } else {
       mv.top.x = mv.top.y = 0;