msm: kgsl: Do a midframe sampling of power stats if enabled

Currently we sample power stats at the expiry of
cmdbatch. In cases where cmdbatch takes a long time
to finish the job, it delays power stats sampling,
in effect it delays DCVS decision for changing the
frequency. Do a midframe power stats sampling and
feed it to DCVS if it is enabled.

Change-Id: I547d792b38649aa1d60525b0dc335791b37989fd
Signed-off-by: Prakash Kamliya <pkamliya@codeaurora.org>