msm: vidc: fix clock rate selection in multiple sessions

Current clock rate selection logic works fine for single
session but for multiple sessions it is not because driver
is not supposed to adjust per session clock rate and add later
but add up all sessions clock rates and adjust later which
will avoid over voting issues in multiple sessions usecase.


Change-Id: Id82f34e71be3821d1b30afe536c5490fe417b407
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>