Add tests for Highbitdepth PSNR metric computations

Change-Id: I07324155f73bbdbe25bb7a7ccd587ebf9010ac7a
diff --git a/vpx_dsp/psnr.h b/vpx_dsp/psnr.h
index e58eb3d..c8da94f 100644
--- a/vpx_dsp/psnr.h
+++ b/vpx_dsp/psnr.h
@@ -51,11 +51,11 @@
                              const uint8_t *b8, int b_stride,
                              int width, int height,
                              unsigned int input_shift);
-#else
+#endif
 void calc_psnr(const YV12_BUFFER_CONFIG *a,
                const YV12_BUFFER_CONFIG *b,
                PSNR_STATS *psnr);
-#endif
+
 int64_t highbd_get_sse(const uint8_t *a, int a_stride,
                        const uint8_t *b, int b_stride,
                        int width, int height);