crypto: msm: optimize ce bandwith scaling

Encryption processing at qcrypto driver includes three main steps:
set ce high bandwidth and enable ce clock in cra_init, then send
encrytion request, and at last set ce low bandwidth and disable
clock in cra_exit. This process is fine for the use case where
there are lots of requests between cra_init and cra_exit, but will
introduce large overhead for mmc layer disk encryption as it calls
cra_init, queue request and cra_exit for every encryption request.

It is not necessary to set low bandwidth and disable clock for every
encrypt request when it is completed. So we delay these scaling down
tasks for a while, and just scale down the last request when timer
expires so as to amortize and decrease the overhead.

Signed-off-by: Zhen Kong <zkong@codeaurora.org>
crypto: msm: fix issues in ce clock disable processing

In the situation of more than one requests, the ce clock may get
errorneously disabled even when there are active requests. The
scaling operation is then modified to fix the problem and ensure
all requests are completed when disable the clock. We also clean
up the related codes.

Signed-off-by: Zhen Kong <zkong@codeaurora.org>