qseecom: change qseecom bus scaling timer operation

To ensure ce clock is not disabled before tz operation is completed,
we delete the old timer when tz side operation begins, and then add
a new timer after tz operation is completed.

Change-Id: I4bc8fe3d9305cc1ed5db8e6490832fcc790ef3d7
Signed-off-by: Zhen Kong <zkong@codeaurora.org>