tools/power turbostat: fix decoding of HWP_STATUS

The "excursion to minimum" information is in bit2
in HWP_STATUS MSR. Fix the bitmask used for
decoding the register.

Signed-off-by: Antti Laakso <antti.laakso@intel.com>
Reviewed-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>