avfilter/x86/vf_gradfun_init: fix const and related warnings

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/x86/vf_gradfun_init.c

@@ -30,7 +30,8 @@
 void ff_gradfun_filter_line_mmxext(intptr_t x, uint8_t *dst, const uint8_t *src,
                                    const uint16_t *dc, int thresh,
                                    const uint16_t *dithers);
-static void gradfun_filter_line_mmxext(uint8_t *dst, uint8_t *src, uint16_t *dc,
+static void gradfun_filter_line_mmxext(uint8_t *dst, const uint8_t *src,
+                                       const uint16_t *dc,
                                        int width, int thresh,
                                        const uint16_t *dithers)
 {
@@ -48,7 +49,7 @@ static void gradfun_filter_line_mmxext(uint8_t *dst, uint8_t *src, uint16_t *dc,
 void ff_gradfun_filter_line_ssse3(intptr_t x, uint8_t *dst, const uint8_t *src,
                                   const uint16_t *dc, int thresh,
                                   const uint16_t *dithers);
-static void gradfun_filter_line_ssse3(uint8_t *dst, uint8_t *src, uint16_t *dc, int width, int thresh, const uint16_t *dithers)
+static void gradfun_filter_line_ssse3(uint8_t *dst, const uint8_t *src, const uint16_t *dc, int width, int thresh, const uint16_t *dithers)
 {
     intptr_t x;
     if (width & 7) {
@@ -62,8 +63,8 @@ static void gradfun_filter_line_ssse3(uint8_t *dst, uint8_t *src, uint16_t *dc,
                                  thresh, dithers);
 }
 
-void ff_gradfun_blur_line_movdqa_sse2(intptr_t x, uint16_t *buf, uint16_t *buf1, uint16_t *dc, uint8_t *src1, uint8_t *src2);
-void ff_gradfun_blur_line_movdqu_sse2(intptr_t x, uint16_t *buf, uint16_t *buf1, uint16_t *dc, uint8_t *src1, uint8_t *src2);
+void ff_gradfun_blur_line_movdqa_sse2(intptr_t x, uint16_t *buf, const uint16_t *buf1, uint16_t *dc, const uint8_t *src1, const uint8_t *src2);
+void ff_gradfun_blur_line_movdqu_sse2(intptr_t x, uint16_t *buf, const uint16_t *buf1, uint16_t *dc, const uint8_t *src1, const uint8_t *src2);
 static void gradfun_blur_line_sse2(uint16_t *dc, uint16_t *buf, const uint16_t *buf1, const uint8_t *src, int src_linesize, int width)
 {
     intptr_t x = -2*width;