power: check frequencies count before filling array

power: check frequencies count before filling array

The freqs array size is RTE_MAX_LCORE_FREQS. Before filling the
array with num_freqs elements, restrict the total num to
RTE_MAX_LCORE_FREQS. This fix aims to fix the coverity scan issue
like:
Overrunning array "pi->freqs" of 256 bytes by passing it to a
function which accesses it at byte offset 464.

Coverity issue: 371913
Fixes: ef1cc88f1837 ("power: support cppc_cpufreq driver")
Cc: stable@dpdk.org
Signed-off-by: Richael Zhuang <richael.zhuang@arm.com>
Acked-by: David Hunt <david.hunt@intel.com>