vp9_encoder: hide adjust_image_stat()

this function is only needed with CONFIG_INTERNAL_STATS

Change-Id: I9c8d16cb9069dd8370f8b30329933c0d97f6d0aa
diff --git a/vp9/encoder/vp9_encoder.c b/vp9/encoder/vp9_encoder.c
index ba38d64..b5d55c8 100644
--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -3962,7 +3962,6 @@
 extern double vp9_get_blockiness(const unsigned char *img1, int img1_pitch,
                                  const unsigned char *img2, int img2_pitch,
                                  int width, int height);
-#endif
 
 static void adjust_image_stat(double y, double u, double v, double all,
                               ImageStat *s) {
@@ -3972,6 +3971,7 @@
   s->stat[ALL] += all;
   s->worst = MIN(s->worst, all);
 }
+#endif  // CONFIG_INTERNAL_STATS
 
 int vp9_get_compressed_data(VP9_COMP *cpi, unsigned int *frame_flags,
                             size_t *size, uint8_t *dest,