tools/power turbostat: Fix /dev/cpu_dma_latency warnings

stable inclusion
from stable-v5.10.177
commit 038765a095fd6dc13128c0d350c53d89ace690dc
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I88YNP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=038765a095fd6dc13128c0d350c53d89ace690dc



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[ Upstream commit 40aafc7d ]

When running as non-root the following error is seen in turbostat:

turbostat: fopen /dev/cpu_dma_latency
: Permission denied

turbostat and the man page have information on how to avoid other
permission errors, so these can be fixed the same way.

Provide better /dev/cpu_dma_latency warnings that provide instructions on
how to avoid the error, and update the man page.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>