x86, msr: Fix typo in ENERGY_PERF_BIAS_POWERSAVE

Fix a trivial typo in the name of the constant
ENERGY_PERF_BIAS_POWERSAVE.  This didn't cause trouble because this
constant is not currently used for anything.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Len Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/tip-abe48b108247e9b90b4c6739662a2e5c765ed114@git.kernel.org