tools/power turbostat: Handle cap_get_proc() ENOSYS

[ Upstream commit d34fe509 ]

Kernels configured with CONFIG_MULTIUSER=n have no cap_get_proc().
Check for ENOSYS to recognize this case, and continue on to
attempt to access the requested MSRs (such as temperature).

Signed-off-by: Calvin Owens <calvin@wbinvd.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>