ASoC: Intel: mrfld: fix uninitialized variable access

Randconfig testing revealed a very old bug, with gcc-8:

sound/soc/intel/atom/sst/sst_loader.c: In function 'sst_load_fw':
sound/soc/intel/atom/sst/sst_loader.c:357:5: error: 'fw' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  if (fw == NULL) {
     ^
sound/soc/intel/atom/sst/sst_loader.c:354:25: note: 'fw' was declared here
  const struct firmware *fw;

We must check the return code of request_firmware() before we look at the
pointer result that may be uninitialized when the function fails.

Fixes: 9012c9544e ("ASoC: Intel: mrfld - Add DSP load and management")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst/sst_loader.c

@@ -354,14 +354,14 @@ static int sst_request_fw(struct intel_sst_drv *sst)
 	const struct firmware *fw;
 
 	retval = request_firmware(&fw, sst->firmware_name, sst->dev);
-	if (fw == NULL) {
-		dev_err(sst->dev, "fw is returning as null\n");
-		return -EINVAL;
-	}
 	if (retval) {
 		dev_err(sst->dev, "request fw failed %d\n", retval);
 		return retval;
 	}
+	if (fw == NULL) {
+		dev_err(sst->dev, "fw is returning as null\n");
+		return -EINVAL;
+	}
 	mutex_lock(&sst->sst_lock);
 	retval = sst_cache_and_parse_fw(sst, fw);
 	mutex_unlock(&sst->sst_lock);