valgrind: Increase timeout duration 30 -> 90 s

Attempt to fix intermittent failure of `drd/tests/std_list`
Locally tested to take around 45 s on qemuarm64

[YOCTO #14228]

Signed-off-by: Yi Fan Yu <yifan.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>