selftests/intel_pstate: fix build for ARCH=x86_64

stable inclusion
from stable-v5.10.156
commit b1619f0307762526949f95c878119ca80e32149d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MCG1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1619f0307762526949f95c878119ca80e32149d



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[ Upstream commit beb7d862 ]

Handle the scenario where the build is launched with the ARCH envvar
defined as x86_64.

Signed-off-by: Ricardo Cañuelo <ricardo.canuelo@collabora.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>