selftests: timers: clocksource-switch: fix passing errors from child

stable inclusion
from stable-v5.10.137
commit 990ca39e78cf4005168d15547a8236b835ed0597
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=990ca39e78cf4005168d15547a8236b835ed0597



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[ Upstream commit 4d8f52ac ]

The return value from system() is a waitpid-style integer. Do not return
it directly because with the implicit masking in exit() it will always
return 0. Access it with appropriate macros to really pass on errors.

Fixes: 7290ce14 ("selftests/timers: Add clocksource-switch test from timetest suite")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: John Stultz <jstultz@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>