avcodec/proresdsp: Make put_pixels truely ptrdiff_t compatible

It currently uses an intermediate int which wouldn't work
if linesize exceeded the range of int and inhibits compiler
optimizations. Also switch to pointer arithmetic and use
smaller scope.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/proresdsp.c

@@ -40,16 +40,14 @@
  */
 
 static inline void put_pixel(uint16_t *dst, ptrdiff_t linesize, const int16_t *in, int bits_per_raw_sample) {
-    int x, y, src_offset, dst_offset;
-
-    for (y = 0, dst_offset = 0; y < 8; y++, dst_offset += linesize) {
-        for (x = 0; x < 8; x++) {
-            src_offset = (y << 3) + x;
+    for (int y = 0; y < 8; y++, dst += linesize) {
+        for (int x = 0; x < 8; x++) {
+            int src_offset = (y << 3) + x;
 
             if (bits_per_raw_sample == 10) {
-                dst[dst_offset + x] = CLIP_10(in[src_offset]);
+                dst[x] = CLIP_10(in[src_offset]);
             } else {//12b
-                dst[dst_offset + x] = CLIP_12(in[src_offset]);
+                dst[x] = CLIP_12(in[src_offset]);
             }
         }
     }