loopback_latency: Fix buffer overflow error

Fix buffer overflow when opening the wav file. It's caused by fread
incorrectly uses file_size (in bytes) when reading shorts. The fix is to
change the fread call to read file_size / sizeof(short).

BUG=b:443098222
TEST=tast run $DUT audio.CrasCaptureLatency.no_effects

Change-Id: I6f77f165d939b348331b18f6c0ddd57a423996a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/audiotest/+/6999089
Auto-Submit: Norman Bintang <normanbt@chromium.org>
Commit-Queue: Baili Deng <bailideng@google.com>
Commit-Queue: Norman Bintang <normanbt@chromium.org>
Tested-by: Norman Bintang <normanbt@chromium.org>
Reviewed-by: Baili Deng <bailideng@google.com>

loopback_latency/common.c

diff --git a/loopback_latency/common.c b/loopback_latency/common.c
index c7eff85..7d770a2 100644
--- a/loopback_latency/common.c
+++ b/loopback_latency/common.c
@@ -109,7 +109,8 @@
   }
 
   // Read the PCM data from the file
-  size_t num_read = fread(*pcm_data, sizeof(short), file_size, file);
+  size_t num_read =
+      fread(*pcm_data, sizeof(short), file_size / sizeof(short), file);
   if (num_read <= 0) {
     fclose(file);
     fprintf(stderr, "Failed to read PCM data from file\n");