selftests/mqueue: Set timeout to 180 seconds

While mq_perf_tests runs with the default kselftest timeout limit, which
is 45 seconds, the test takes about 60 seconds to complete on i3.metal
AWS instances.  Hence, the test always times out.  Increase the timeout
to 180 seconds.

Fixes: 852c8cbf ("selftests/kselftest/runner.sh: Add 45 second timeout per test")
Cc: <stable@vger.kernel.org> # 5.4.x
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>