rstream: validate client type from client

Checks if the client type from clients is valid to prevent invalid
buffer access.

BUG=1159255
BUG=b:175764776
TEST=FEATURES=test USE=asan emerge-$BOARD -j adhd
TEST=oss-fuzz

Change-Id: I56e367b2f6b99da2fa4b2725a67772fff625aba2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/2674499
Commit-Queue: Chih-Yang Hsia <paulhsia@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Tested-by: Chih-Yang Hsia <paulhsia@chromium.org>
Reviewed-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Auto-Submit: Chih-Yang Hsia <paulhsia@chromium.org>
2 files changed