cpupower: Fix build error in cpufreq-info

Fix the following build error by including limits.h -

utils/cpufreq-info.c: In function ‘get_latency’:
utils/cpufreq-info.c:437:29: error: ‘UINT_MAX’ undeclared (first use in
this function)
  if (!latency || latency == UINT_MAX) {
                             ^
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Fixes: e98f033f (cpupower: fix how "cpupower frequency-info" interprets latency)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>