tools/power turbostat: correct dumped pkg-cstate-limit value

HSW expanded MSR_PKG_CST_CONFIG_CONTROL.Package-C-State-Limit,
from bits[2:0] used by previous implementations, to [3:0].
The value 1000b is unlimited, and is used by BDW and SKL too.

Signed-off-by: Len Brown <len.brown@intel.com>