devfreq: memlat: Change number of array elements for holding core_stats

Memlat driver allocates as many array elements in core_stats array as 
many possible cpus While when any of core is not available in between
we need to consider what is first and last cpu in possible mask, 
accordingly initialize the core_stats array.

Change-Id: I26420d2b061b712f94c3e496cff12811ea4a678a
Signed-off-by: Avaneesh Kumar Dwivedi <quic_akdwived@quicinc.com>