selftests/tls: Add {} to avoid static checker warning

mainline inclusion
from mainline-v5.14-rc1
commit f50688b4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I56S5K?from=project-issue

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f50688b47c5858d2ff315d020332bf4cb6710837



--------------------------------

This silences a static checker warning due to the unusual macro
construction of EXPECT_*() by adding explicit {}s around the enclosing
while loop.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 7f657d5b ("selftests: tls: add selftests for TLS sockets")
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>