package/linux-tools: some selftests needs util-linux schedutils

package/linux-tools: some selftests needs util-linux schedutils

Some kernel-selftests are using taskset program, so make sure that
BR2_PACKAGE_UTIL_LINUX_SCHEDUTILS is selected.

[linux-4.19 selftests]$ git grep taskset
bpf/test_progs.c:       assert(system("taskset 0x1 ./urandom_read 100000") == 0);
cpu-hotplug/cpu-on-off-test.sh: taskset -p 01 $$
cpufreq/main.sh:        taskset -p 01 $$
netfilter/nft_trans_stress.sh:        ip netns exec "$testns" taskset $mask ping -4 127.0.0.1 -fq > /dev/null &
netfilter/nft_trans_stress.sh:        ip netns exec "$testns" taskset $mask ping -6 ::1 -fq > /dev/null &
rcutorture/bin/jitter.sh:       if ! taskset -p $cpumask $$ > /dev/null 2>&1

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>