pan/decode: detect error on fseek

We do this for other calls to fseek here, so let's be consistent.

CID: 1659325
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36724>

src/panfrost/tools/panfrostdump.c

@@ -358,7 +358,10 @@ main(int argc, char *argv[])
                   return EXIT_FAILURE;
                }
 
-               fseek(data_fp, doh.file_offset, SEEK_SET);
+               if (fseek(data_fp, doh.file_offset, SEEK_SET)) {
+                  perror("fseek error");
+                  return EXIT_FAILURE;
+               }
 
                nbytes = fread(bos[j], 1, doh.file_size, data_fp);
                if (nbytes < doh.file_size) {