msm: lpm-levels: Fix cpu votes for lpm-level nodes

When kernel is booted with lesser than max cpus possible, the lpm
levels' cpu mask does not account for hotplugged cores to be able to
enter a cluster/system low power mode. Fix by accounting for offline
cpus in the levels structure.

Change-Id: Icca70bf64d9faa511ce8611507101889051702a7
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>