PM / devfreq: memlat: increment mon count for compute mons

Today, compute mons do not increment the inited mons count.
Reorganize the mon probe function to make sure that they do.

Change-Id: Ia93e419a4e3e14c8e238c66630c27699ff4e0cbc
Signed-off-by: Amir Vajid <avajid@codeaurora.org>