ffhash: Change size to an int

This fixes compilation with MSVC and ICL, and makes ffhash consistent
with how the rest of the codebase uses read().

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

tools/ffhash.c

@@ -87,7 +87,7 @@ static int check(char *file)
 
     av_hash_init(hash);
     for (;;) {
-        ssize_t size = read(fd, buffer, SIZE);
+        int size = read(fd, buffer, SIZE);
         if (size < 0) {
             close(fd);
             finish();