tools/power turbostat: fix dump for AMD cpus

turbostat --Dump exits early with status 243 (-13)

get_counters() calls get_msr_sum() on zen CPUS
for MSR_PKG_ENERGY_STAT, but per_cpu_msr_sum
has not been initialized.

Signed-off-by: Dan Merillat <git@dan.eginity.com>
Signed-off-by: Len Brown <len.brown@intel.com>