intel: gen decoder: don't check for size_t negative values

We should get either 0 or 1 here.

CID: 1373562 (Control flow issues)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: Matt Turner <mattst88@gmail.com>

src/intel/common/gen_decoder.c

@@ -648,7 +648,7 @@ gen_spec_load_from_path(const struct gen_device_info *devinfo,
    do {
       buf = XML_GetBuffer(ctx.parser, XML_BUFFER_SIZE);
       len = fread(buf, 1, XML_BUFFER_SIZE, input);
-      if (len < 0) {
+      if (len == 0) {
          fprintf(stderr, "fread: %m\n");
          fclose(input);
          free(filename);