msm: lpm-levels: optimize cluster and cpu_freq traces

TRACE_EVENT() increases the footprint of the kernel.
cluster and cpu_freq enter and exit trace definitions
are using same structured data and arguments.
So replace with DECLARE_EVENT_CLASS to reuse and share
their functions and structures.

Change-Id: I67c661d02d991a00bd1f6da118b7eb0b6d2ae658
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>