tools/power/turbostat: Fix a knl bug

tools/power/turbostat: Fix a knl bug

[ Upstream commit 137f01b3529d292a68d22e9681e2f903c768f790 ]

MSR_KNL_CORE_C6_RESIDENCY should be evaluated only if
1. this is KNL platform
AND
2. need to get C6 residency or need to calculate C1 residency

Fix the broken logic introduced by commit 1e9042b9c8d4 ("tools/power
turbostat: Fix CPU%C1 display value").

Fixes: 1e9042b9c8d4 ("tools/power turbostat: Fix CPU%C1 display value")
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>