msm: vidc: Adds clock scaling

Video driver manages clock rate according
to the increase in load on video core. Clock
is scaled as per number of macroblocks
decoded/encoded per second. This makes sure
that the power consumption and performance is
optimal.

Change-Id: If8aede0e3048cdc9bcdf14ce0c239a58bdd5d263
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>