Remove unused get_psnr() prototype

Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/dsputil.h

@@ -687,11 +687,6 @@ void ff_mlp_init_x86(DSPContext* c, AVCodecContext *avctx);
 #   define LOCAL_ALIGNED_16(t, v, ...) LOCAL_ALIGNED(16, t, v, __VA_ARGS__)
 #endif
 
-/* PSNR */
-void get_psnr(uint8_t *orig_image[3], uint8_t *coded_image[3],
-              int orig_linesize[3], int coded_linesize,
-              AVCodecContext *avctx);
-
 #define WRAPPER8_16(name8, name16)\
 static int name16(void /*MpegEncContext*/ *s, uint8_t *dst, uint8_t *src, int stride, int h){\
     return name8(s, dst           , src           , stride, h)\